Guido Petrucci
email: guido.petrucci@cereve.enpc.fr

A methodology to assess sustainability of urban stormwater management

Keywords: Urban stormwater management, source control, hydrological models, sustainability, Best Management Practices

Urban stormwater management (USWM) in developed countries is undergoing a significant evolution. Centralized systems are giving place to distributed facilities, mainly to cope with flooding caused by fast urban growth and with water bodies' quality degradation. This evolution has to face inertias from existing structures, but it relies on the idea that new strategies are more sustainable than old ones. We assume that USWM is strongly dependent on local conditions and objectives, and thus its sustainability has to be evaluated at a local scale.

Although no global solution can be found, it is worth defining a general method to assess if an USWM strategy is sustainable on a specific site. In this paper we propose and discuss a methodology of this kind, mainly based on hydrological models. The methodology is made of three phases: definition of sustainability; modelling and analysis of several case studies; generalization procedure.

INTRODUCTION

Urban stormwater management (USWM) is undergoing a significant evolution. While in the last 150 years the main strategy was to centralize and evacuate as fast as possible urban stormwater through combined or separate sewers, in the last two decades the interest in source control has grown (Niemczynowicz, 1999;Novotny and Brown, 2007).

The two main drivers of this evolution, at least in countries where traditional sewers are diffused, are (i) the awareness that urban stormwater contributes significantly to water bodies' pollution, (ii) the inertia of traditional structures (i.e. both sewer systems and their management institutions) to adapt to new needs. In particular, increases in runoff due to fast urban growth are often impossible to manage without extremely expensive renovations of existing structures. Among the authors pointing out these problems, see for example Chocat et al., 2007. The basic principles of source control are in opposition to the traditional one: stormwater must be managed, and eventually reused, as close as possible to its falling site, to do not aggravate the situation elsewhere; natural fluxes must be preserved and restored, particularly toward groundwater; runoff must be slowed down. Another principle often stated is to keep water on surface, integrated to urban systems, in order to improve social awareness and to provide urban amenities.

9th World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters: resource or risks? 26-30 October 2009 2 / 10 These principles are realized through a wide set of usually small technical solutions, like retention tanks, vegetated strips, infiltration basins, ponds, etc. Two examples are shown in figure 1. These solutions are collectively addressed, especially in U.S. literature, as Best Management Practices (BMPs). Other denominations exist, referring to the same principles but putting the accent on different aspects, like SUDS (Sustainable Urban Drainage Systems) or LID (Low Impact Development). Source control is generally considered "greener" and more sustainable than traditional USWM, and researches on it are oriented to assess more its effectiveness in reducing runoff and pollutants than its overall performance. But, as discussed below (Discussion Section), sustainability of a particular USWM system is strongly dependent on its context, and it can not be affirmed in a general way. Therefore, under which conditions source control is "better" than centralized sewers? Moreover, most of the applications of source control techniques are still confined to small experimental areas. In a scenario of large diffusion of source control, does it have to replace completely traditional systems, or just to be complementary to them? To what extent? In which cases? At which scale it has to be managed?

To answer these questions about global impacts of source control, both in specific and general cases, a methodology is necessary to assess the sustainability of alternative USWM options. The purpose of this paper is to propose a methodology of this kind.

After a brief overview on Material and Methods, we discuss the main issues (Results and Discussion) posed by a similar assessment. Then, we finally propose a methodology made of three phases: first, a definition of sustainability; second, a modelling and analysis of several case studies; third, a generalization procedure.

MATERIAL & METHODS

The proposed methodology uses hydrological and hydraulic integrated models in its second and third phase, as described below. Many models are available, both commercial and researchoriented, with different characteristics. For each application one suitable model should be selected a priori or after a comparison with others. For the second phase, the author uses SWMM 5 (Rossmann, 2004) and STORM (IPS, 2008), that have complementary capacities. To realize the automation part of the third phase, our intention is to use Matlab programming.

RESULTS AND DISCUSSION

General sustainability assessment: main issues

In this section we shortly describe the main issues that have to be taken into account by a comprehensive methodology for USWM sustainability assessment.

Local dependency on physical and social context

If stormwater management can be necessary in every urban setting, it has to be implemented differently in each one. Stormwater regime is dictated by climatic conditions; rainfall-runoff transformation depends on topography, geology and land use; available management alternatives are based on urban form and pre-existing structures, etc (Pitt and Clark, 2008). Furthermore, the social context where the USWM is developed affects the objectives that have to be aimed by the system and their priority. Thus, there is neither a general formulation nor a general solution to sustainable urban stormwater problem.

The main implication of this local dependency of USWM is that it is not possible (or at least not logically correct) to assess the sustainability of a solution in general, but only in a specific context. The definition of durability proposed later in this paper, will take into account this characteristic.

Variety of alternatives

In a traditional approach to USWM, the alternative solutions to a problem are generally a few "big" structures, with some alternative locations and with an optimisation to be done for dimensioning and eventually operation. In a source control approach to the same problem, the number of independent structures (a priori of different typologies) can be huge, the location becomes a territorial distribution and the dimensioning must be done for each one.

The definition of alternatives to be considered in the analysis is then a delicate issue and, although computer and algorithm innovations offer potential solutions, traditional optimisation instruments have to be reviewed (Pitt and Clark, 2008).

Complexity of involved physical phenomena

Shifting the interest from pipes flow capacity to open surfaces potential to infiltrate and stock water, we shift the emphasis from hydraulics to hydrology. The problem is that hydrology does not dispose, nowadays, of specifically developed instruments for urban areas. The traditional approach of this discipline is focused on much bigger scales (typically river watersheds), and the transposition to smaller ones is not always satisfying (Niemczynowicz, 1999). Indeed, also if elementary phenomena can be the same, intrinsic dishomogeneity of urban environment greatly increases the complexity of flow paths. Moreover, as in urban settings we usually consider a 9th World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters: resource or risks? 26-30 October 2009 4 / 10 much smaller scale, the requested accuracy in flow estimations is often 2-3 orders of magnitude bigger (e.g. l/s instead of m 3 /s).

While waiting for a new approach to urban water processes, we can use and adapt classical hydrological models, but we have to accurately validate hypothesis and parameters and to carefully handle results.

Non-technical complexity USWM system, as part of an urban context, is integrated to many others (technical or not). Thus, its correct implementation and operation depends upon a wide set of exogenous variables. For example, a same technical solution can perform well or not according to citizens' collaboration.

Another example is that it can be impossible inside an administrative area to set an hydrologically-sound variable policy, because of the economic inequality it generates. This kind of complexity appears typically when studying real cases (e.g. Maytraud et al., 1995), or when trying to apply theoretical results to real systems. In some cases, such difficulties can be important enough to turn a good theoretical alternative into an inapplicable or inefficient one.

Behaviour evolution over time

Little knowledge is available and trustful about how source control systems get old. Wellplanned maintenance can prevent most dysfunctions of a system and keep it efficient, but maintenance is difficult to assure (Guillon et al., 2008). Moreover, phenomena like soil compaction or pollutant accumulation are hardly avoidable and poorly known (see for example the results of Emerson and Traver, 2008). Even less is known about long term maintenance: after how many years a source control element has to be completely renovated?

The behaviour evolution over time is a good example of lack of knowledge about source control. Its solution would require years of empirical researches and therefore exceeds the purpose of this paper. Nevertheless, we have to take this uncertainty into account in our methodology: it imposes to consider different ageing and dysfunction scenarios while estimating the long-term efficacy of a source control system.

Sustainability evaluation: methodology proposal

The methodology we propose to evaluate USWM tries to cope with the described issues, and it is composed by three main parts:

-a general framework to define sustainability, declinable for any specific case; -the analysis of a set of real specific cases, in order to validate the sustainability definition, assess models' validity and create a casuistic of contexts; -an attempt to generalize results using models.

Actually, at LEESU, the review and validation of the first part is in progress, and the second one has started.

First phase: a general framework to define sustainability

The concept of sustainable development, thanks to its generality, is used in many contexts with different meanings. Its most known definition is the one from the 'Brundtland Report' (United Nations, 1987): "[development] which meets the needs of the present without compromising the ability of future generations to meet their own needs". This extremely synthetic definition, although effective, is not directly operational and needs to be transposed to each specific field of application. This can be done by declining for each object the economic, environmental and social values. The underlying idea is that, while economic value decreases in time and the far future monetary values are irrelevant, social and environmental values should take into account the future as much as the present, satisfying in this way the Brundtland's definition.

More in detail, it is accepted that for a sustainable decision making it is necessary, although not sufficient, to explicit all objectives involved in the decision, including environmental and social ones. Following this approach, we adapt the criteria-tree from the Daywater project (explained below) in order to base our definition of sustainability.

Daywater and Daywater 2 are projects aiming to create an Adaptive Decision Support System (ADSS) to solve problems of stormwater management recurring to BMPs (Thévenot, 2008). One of the elements developed in the ADSS is the criteria-tree: for six criteria (technical, operation & maintenance, environmental, social & urban community benefits, economic, legal & urban planning) a nearly exhaustive structure of sub-criteria and suggested indicators is given. It is a set of evaluation criteria and methods general enough to fit (through an adaptation process) a large extent of specific cases (Deutsch and Deroubaix, 2008). In table 1 an example for the Technical criteria is presented. We can consider that the six criteria are general enough to be mostly universal (i.e.: they are pursued, in some degree, by each USWM system). To fit a specific case we have to move upward the tree: we have (i) to choose the sub-criteria that best represent the specific issues to be solved and the existent constraints, discarding the non-relevant aspects. Then, (ii) for each chosen sub-criterion, we have to take one or more relevant indicator and, (iii) for each indicator we have to define an evaluation procedure (expert estimation, modelling, etc). For our purpose, i.e. to well define case-specific sustainability, if the fitting procedure is done well, the resulting set of indicators can be considered an exhaustive description of the problem, explicitly setting all its local aspects.

One expected result of the testing work in progress is a completion of the criteria-tree with a suggested method for measuring and assessment for each indicator proposed. In the Daywater ADSS such methods are listed but not linked to specific indicators.

It is necessary to point out that, even if many aspects are common and can be shared, the sustainability assessment can not be considered a decision support procedure. In fact, some key divergences subsist. For example no stakeholder is involved in the assessment, so the indicators represent a description of reality made by the analyst and not, as in decision making, the interests of parts. Another example is that neither preference aggregation nor negotiation procedures are comprised in our assessment.

Second phase: empiric evaluation on case studies

The purpose of this phase is threefold: validating the framework; finding indicators' estimation methods -especially models; create the support for the generalization attempt.

In the analysis we insist on modelling, for two practical reasons: (i) most of the objectives of USWM can be assessed through a hydrologic/hydraulic model; (ii) if the model is trustful (and this will be verified through the validation), it is an optimal way to carry out the generalization.

The case studies constitute the main support of all the methodology: they provide knowledge about involved phenomena and they define the validity limits of framework and models. Thus, a priori, the greater is the number of case studies considered, the better will be the understanding of phenomena and the generality of the conclusions. On the other hand, the number of treatable case studies is limited by available resources. In order to obtain the better result, it is important to carefully choose the cases to analyse. The most important characteristics for this choice are: variety of territorial scales (from the block to the district or to the city), variety of contexts (climate, hydrogeology, urban structure, objectives, etc), variety of applied BMPs, availability of hydrologic measures and feedbacks on performances, possibility of collaboration with local experts.

After a case study is selected, the analysis procedure follows these points: 1. Framework fitting to define local sustainability, together with assessment methods for each indicator. 2. Hydrologic/hydraulic model fitting. The "situation", pre-or post-BMPs installation, to use in the fitting phase depends mostly on measures availability. 3. Validation of the fitted model, with additional measures in the same "situation". 4. Test of the fitted model with/without applied BMPs (i.e. the "situation" not considered for fitting). 5. Assessment of all the indicators for the two "situations", recurring to long time-series, eventually synthetic. Calculation of indicators' variations.

6. Eventually, simulation of significant USWM alternatives other than the two already considered. 7. Analysis of results and retrofitting to framework, model and other assessment procedures.

Remarks on the procedure:

-Model fitting phase, which can be carried out with suitable algorithms (e.g.: Franchini et al., 1998), helps to verify if literature's hydrological standard parameters (e.g. those presented in Appendix A of Rossmann, 2004) are able to describe urban setting, or if they need corrections. We refer here to the issue "complexity of involved physical phenomena" described above. -Although a specific phase of global retrofitting is explicit in the procedure, partial retrofits can be done at any point and for any object (framework, indicators, etc), especially when, for the first case studies, the methodology in itself is tested. Moreover, in these first tests, many indicators and models can be tried in parallel and compared.

Third phase: generalization

This last phase has the purpose of comparing alternative USWM solutions for a wide range of conditions and sustainability definitions. Although its contents will greatly repose on the preceding phase, it is possible to define its development under some reasonable hypothesis.

The main activities will be (i) to create a set of alternative scenarios, each composed by a context and a sustainability definition, (ii), to cross them with a set of alternative USWM systems, (iii) to fit and run models and (iv) to assess indicators. A simplified schema is presented in figure 2. The first problem to solve is the creation of fictive contexts: each one has to be described by a set of significant "key-variables" that drive USWM performances. The choice of this set of pertinent key-variables is not obvious, as they have to satisfy many requirements. In facts, these variables must (i) describe quite in detail the urban and physical context (climate, hydrogeology), (ii) allow discrimination between different USWM systems, (iii) be easily transposable to the model and (iv) their number must be as small as possible. The choice of this set of key-variables has to be done on the basis of the experience from case studies, but also in function of the model employed.

Once the key-variables are selected, together with their range and possible values, it is possible to generate scenarios through variables combination. Basically, the exhaustive set of available scenarios can be obtained by Cartesian product of all the definition-sets of the key-variables. To obtain a finite set of scenarios it will be necessary to discretize continue definition-sets, and to bound infinite ones. The approach to use for each variable has to be decided case by case.

The opportunity of an exhaustive or a selected review of the set of scenarios will depend on their number and on the time requested to analyse each one. A priori, the big number of expected scenarios (for n variables with 10 values each, the total number of scenarios is 10 n ) suggests that a selection will have to be done, on a basis of pertinence and significance of scenarios. The use of typical climate, urban forms and topographies from specific world areas or, eventually, of a research algorithm, could simplify the exploration of the scenarios' set.

Also for sustainability definitions, a combinatory approach can be used: as we consider that sustainability estimation is a subset of the whole set of indicators considered, it is possible to extract all the subsets and to assess them on all scenarios. In this case too, the exhaustive approach seems pointless, as many resulting definitions have limited interest. Thus, a selection strategy has to be defined to discard unrealistic definitions.

As described in the issues' paragraph of this paper, one sensible point of this methodology is the procedure to define USWM alternatives to be considered. This point is still object of research.

The main difficulty is that, as such procedure cannot be exhaustive (as discussed above, we have to cope with a series of spatial distribution) and it has to be automatic (to allow the treatment of a large number of scenarios), we need to find an algorithm capable to efficiently select a small number of good alternatives in a high dimensional space. A possible solution is to create an expert system trained over case studies and researchers' experience.

In conclusion, it is necessary to remember that any result obtained in this phase, independently from the chosen procedure, pass through the model and the objectives' assessment. Therefore, any result can be considered valid and trustful only in the validity field of the model. Also if the presented methodology is theoretically valid, practically the fictive scenarios will have to be chosen in "neighbourhoods" of the case studies.

CONCLUSIONS

This paper proposes a methodology to solve the problem of sustainability assessment for USWM systems using source control, both in specific and general cases. The methodology is articulated in three phases.

The first phase is the setting of a sustainability definition. We adopt a general criteria-tree and a method to apply it to site-specific problems.

The second phase is the sustainability assessment for a series of case studies. For each one a specific definition of sustainability is given, and measured through existing data and modelling.

A validation of the framework, of the models and of the assessment procedure is done.

The third phase consists in a generalization of the results obtained. A set of theoretical scenarios is constructed and modelled, in order to assess the sustainability of USWM systems in a wide range of conditions.

The methodology described can cope with many issues inherent to the complexity of USWM systems although, due to these issues, the validity of the general results obtained will be strongly dependent on the case studies considered. Moreover, some described task which has not yet been performed is still to define in detail, and can bring unexpected difficulties. In particular, the study of real cases can always bring unpredicted new elements to the analysis, and the third phase includes some innovative and non-straightforward practical, technical and mathematical operations. We can expect that, at least at the beginning, the scope of the methodology will have to be reduced, for example to a restrained set of significant indicators. The general formulation proposed stands anyway as a valid theoretical reference and, if the first tests will give adequate results, as the methodology permits feedbacks and further extensions, oriented improvements can be foreseen. 08-WWW- YES-2009-Brazil-Petrucci-Paper-2009-09-14.doc

Figure 1 -

 1 Figure 1 -Two examples of BMPs in France: a rainwater harvesting tank at the parcel scale in Champigny (Val-de-Marne), and an infiltration/overflow basin for a block of houses in Noisy-Le-Grand (Seine-St-Denis)

Figure

  Figure 2 -Schema of the generalization phase

Table 1 -Technical criteria tree from the Daywater ADSS ( http://daywater.in2p3.fr/EN/ )

 1

	Criteria			Sub-criteria			Indicators
								Design storm return interval storage volume (m3/ha)
								Response rate for superimposed critical storm durations
		Flood Control		Storage and flood control		(m3/ha/hr) Ratio of storage to contributing drainage area (ratio) Number of floods per year within catchment (1...n) Overflow frequency and duration (1...n) Discharge or throttle rate (m3/s) Uniform flow distribution (H/M/L)
								Length of antecedent dry periods ()
	Technical	Pollution System flexibility & potential	Control for retrofitting		Water quality Capability for change over	treatment time		Pollutant concentration probability exceedance for given target levels (% exceedance for given target level) First-flush capture potential (10/15mm effective runoff treatment for all storms) (mm runoff/av storm event) %age pollution capture for given RI storms and retention times (% capture for given RI or retention time) Design freeboard for storage and water quality change (%; m3/lifetime) Ease of retrofitting and modification (H/M/L) Costs of retrofitting and add-on structures/features (Euro (av.cost)) Potential to recycle system components/waste (H/M/L) Reliability (H/M/L) Durability (H/M/L)
		Impact on drainage	system	Integration	with Design	existing life	system	Flow reduction to STP and CSOs (%; m3) Reduction in stormwater flows (%; m3/ha) Operational lifetime (Years) Sedimentation rates and storage volume (m3/yr; % reduction in storage volume/yr)

  Indoor and Built Environment, vol. 16, no. 3, pp. 273-285. • EMERSON C.H. and Traver R.G. (2008). Multiyear and Seasonal Variation of Infiltration from Storm-Water Best Management Practices. J. Irrig. and Drain. Engrg., Vol. 134, Issue 5, pp. 598-605. • FRANCHINI M., Galeati G. and Berra S. (1998). Global optimization techniques for the calibration of conceptual rainfall-runoff models. Hydrolog. Sci. J., 43, 443-458. • DEUTSCH J.C. and Deroubaix J.-F. (2008). Libraries. In: Daywater: an adaptive decision support system for urban stormwater management, Thévenot D. R. (ed.), Ch. 5, IWA Publishing. • GUILLON A., Kovacs Y., Lovera M. and Sénéchal C. (2008). Investigation on how "Control" of Source-Control facilities is organized in France. In: 11th International Conference on Urban Drainage, Edinburgh, Scotland, UK. • IPS (2008). STORM Manual. Ingenieurgesellschaft Prof. Dr. Sieker mbH. Berlin. • JACOB J.S. and Lopez R. (2009). Is Denser Greener? An Evaluation of Higher Density Development as an Urban Stormwater-Quality Best Management Practice. Journal of the American Water Resources Association, Vol. 45, No. 3, pp. 687-701. • MAYTRAUD T., Perez-Sauvagnat I., Breuil B. (1995). Le service public et la promotion des techniques alternatives, trois contre-projets pour avancer. In : Proceedings of Novatech 95, GRAIE, Lyon, pp. 463-470. • NIEMCZYNOWICZ J. (1999). Urban hydrology and water management -present and future challenges. Urban Water, Volume 1, Issue 1, March 1999, Pages 1-14, ISSN 1462-0758. • NOVOTNY V. and Brown P. (2007). Cities of the future: The fifth paradigm of urbanization. In: Cities Of The Future: Towards Integrated Sustainable Water And Landscape Management, Novotny V. and Brown P. (ed.), IWA Publishing, London, UK, pp. xiii-xxiv. • PITT R. and Clark S. E. (2008). Integrated Storm-Water Management for Watershed Sustainability. J. Irrig. and Drain. Engrg., Vol. 134, Issue 5, 548-555. 9th World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters: resource or risks? 26-30 October 2009 10 / 10 • ROSSMANN L.A. (2004). Storm water management model User's manual version 5.0. U.S. EPA, Water Supply and Water Resources Division, National Risk Management Research Laboratory, Cincinnati. • THEVENOT D. R. (2008). Daywater: an adaptive decision support system for urban stormwater management. IWA Publishing. • THORNDAHL S. and Schaarup-Jensen K.(2007). Comparative analysis of uncertainties in urban surface runoff modelling. In: Proceedings of 6 th Novatech, GRAIE, Lyon, pp. 1631-1638. • United Nations (1987). Report of the World Commission on Environment and Development, General Assembly Resolution 42/187, 11 December 1987.

REFERENCES

• CHOCAT B., Ashley, R., Marsalek, J., Matos, MR, Rauch, W., Schilling, W.,

Urbonas, B. (2007)

. Toward the Sustainable Management of Urban Storm-Water.


Antoine Van De Voorde
email: antoine.van-de-voorde@cereve.enpc.fr

Ghassan Chebbo

Marie-Christine Gromaire

Rainwater harvesting: What are the potential effects of roof maintenance on runoff quality? France as an example

Keywords: Rainwater harvesting, Re-use, Roof runoff, Biocides

Currently rainwater harvesting is more and more popular in the world. The aim is reduce drinking water consumption in developed countries or create a point of access for water in developing countries, for drinking water or for plants irrigation. For developed countries the problems of rainwater re-use can be linked with micro pollutants contamination. Hence we underline a possible source of biocides and especially of quaternary ammoniums in rainwater stocked, which can be a source of exposition. For developing countries the problematic is link with health by drinking water access. Indeed some authors showed how contaminated rainwater is. Not really by chemical products but by bacteria.

INTRODUCTION

Nowadays, rainwater harvesting and re-use are more and more encouraged, mainly for countries where water resources are rare, since they may prove to be a possible solution. As such, a lot of systems have been created to collect these waters. Moreover in some countries like France, tax reductions have been set up to promote rainwater harvesting ntoine and furthermore the use of these waters in house has been authorized (Governmental decision, 08/21/08). The matter pertains more to the diminution of drinking water and not its access issues. Nevertheless, no studies have been undertaken to evaluate the possible contamination of roof runoff. Indeed it is known that roof materials can be a source of trace metals [START_REF] Robert-Sainte | Contribution des matériaux de couverture à la contamination métallique des eaux de ruissellement[END_REF] or organic micro-pollutants [START_REF] Burkhardt | Biocides used in building materials and their leaching behavior to sewer systems[END_REF]. Furthermore, in developing countries, some studies have begun to establish the current level of rainwater contamination. As a matter of fact, before drinking rainwater is made possible, it has to undergo verifications in order to meet the water quality guidelines for drinking water. Indeed, especially on order to drink rainwater, it is essential to verify that this water meets the guidelines of water quality for drinking water.

MATERIAL & METHODS

We used a methodology divided into 2 parts (Van de [START_REF] Van De | Stockage / Utilisation des,eaux de pluie : Quelle(s) incidence(s) des pratiques d'entretien des toitures sur la qualité et le potentiel d'usage des eaux de ruissellement[END_REF]. Firstly, we listed as exhaustive as possible the different products for roof treatment. This was realized thanks to Internet and visits to hardware stores. After listing all of these products, it has been possible to define the practices linked with the utilization of these products. Furthermore, with the Security Data Sheets (SDS) of the listed products, we were able to determine the molecules used as biocides. Thence we searched in scientific literature to evaluate the toxicity of these compounds and the related risks. After this part, a survey has been conducted to infer about the success of the roof treatment and thus professionals were interrogated. We used a classic approach by poll to comprehend precisely how a roof treatment was undertaken. Finally, we made research on literature in order to have a description of systems used in developing countries, the contamination level of the rainwater collected and the purpose of rainwater harvesting.

RESULTS AND DISCUSSION

Situation in France

Methods of treatment

Concerning roof cleaning, 4 techniques have been identified: primary cleaning, fungicide treatment, waterproofing and paint. The Table 1 presents the number of products for each practice. As we can see the market analysis shows a larger offer for fungicide treatment, with a wider variety of available products (18/32). Waterproofing is also well represented (7/32). This has been verified not only on commercial web sites but also in hardware stores. These results have been proved by the poll for professionals. Indeed, it reported that the most important treatment realized is fungicide treatment which is illustrated in the Figure 1. As we can see, primary cleaning is not present in this figure. Actually these treatments are included in fungicide products used by professionals. In addition, paint is the less used treatment.. This can be explained by the fact that painting induces a fusion of all tiles which can prove to be a huge problem for the future roof maintenance (e.g. substitution of tiles).

Unfortunately, this poll cannot be considered as fully representative due to the contribution of only 7 professionals. Hence, caution was the main concern when dealing with the conclusions.

As a result we isolated the most important technique used: fungicide. Subsequently, the molecules present in the products were identified.

Biocides used

With product tags and SDS, the compounds acting as biocide molecules were listed, of which one family of molecules was pointed out: the Quaternary Ammonium Compounds (QACs). These molecules are constituted by a central Nitrogen atom linked with 4 alkyl chains yielding into a permanent positively charged Nitrogen atom. The general QAC scheme is as follows in Figure 2: We can see that the nature of the different groups can vary. For fungicide products, the molecule used is the alkylbenzyldimethylammonium chloride, called benzalkonium or in short, BAC. Benzalkonium is more and more used in disinfectants, for preservatives or in household products [START_REF] Kummerer | Analysis of benzalkonium chloride in the effluent from European hospitals by solid-phase extraction and high-performance liquid chromatography with post-column ion-pairing and fluorescence detection[END_REF]. This molecule is declared as dangerous for aquatic environment. Indeed its biocide properties can among others destroy bacteria [START_REF] Kummerer | Use of chemotaxonomy to study the influence of benzalkonium chloride on bacterial populations in biodegradation testing[END_REF][START_REF] Sutterlin | The toxicity of the quaternary ammonium compound benzalkonium chloride alone and in mixtures with other anionic compounds to bacteria in test systems with Vibrio fischeri and Pseudomonas putida[END_REF], algae, fish and also crustacean, with EC50 from 280µg/L for fish to 5.9µg/L for crustacean [START_REF] Epa | Registration Eligibility Decision for Alkyl Dimethyl Benzyl Ammonium Chloride[END_REF]. Moreover, QACs are generally allergen upon mere contact on the human skin causing irritations. (INRS, 2005). Furthermore it has been reported that some people can have asthmatic reactions [START_REF] Hemery | Quaternary ammonia and occupational diseases[END_REF], Sènécal-Fouquoire, et al., 2001). Hence, upon treating his roof, a private individual storing rainwater will only collect roof runoff contaminated by quaternary ammoniums compounds. Consequently, not only could this create a risk for the user (e.g. if he washes his car) in producing an allergy, but also in sewers, in wastewater treatment plants or in rivers due to the biocide effects of the molecule.

General formula R 3 N + R 4 R 2 R 1 Cl - Alkylbenzyldimethylammonium (n° CAS : 8001-54-5) N + C H 3 CH 3 C n H 2n+1

Developing countries

The third part of Target 1 of the Millennium Development Goals (MDG) is to halve, by 2015, the proportion of people without sustainable access to safe drinking water and basic sanitation. The MDG has been adopted by 192 United Nation member states and at least 23 international organizations. In this light, rainwater harvesting is a good way to collect and store drinking water on a small-scale (Mwenga [START_REF] Kahinda | Domestic rainwater harvesting to improve water supply in rural South Africa[END_REF]. Moreover, this technique is not a new concept in Africa. As describes Duncker (2000), in KwaZulu-Natal and the Eastern Cape (South Africa), rainwater is the major source of drinking water during rainy season. These systems are more developed in rural area. Gleick showed in 1996, that it existed a link between clean water access and adequate sanitation and diseases propagation. Consequently it is essential to evaluate the bacterial as well as chemical quality of rainwater stocked.

In this domain, a review of Mwenga [START_REF] Kahinda | Domestic rainwater harvesting to improve water supply in rural South Africa[END_REF] shows that some studies underline that the quality follows the international guidelines of drinking water, whilst others prove the poor quality level of rainwater.

For the contaminations, studies have been undertaken all over the world. For example, in New Zealand, [START_REF] Simmons | Contamination of potable roof-collected rainwater in Auckland, New Zealand[END_REF] lead a work to measure trace metals and bacteria in rainwater.

The contamination level for trace metals met the New Zealand drinking water quality guidelines.

Nevertheless the bacteriology proved to be too high to declare the water drinkable according to World Health Organization. Similar results have been found in India (C-3 Report, 2000). Indeed the conclusions of this report were that the bacteriological factor meets the guideline in only 10% to 70% of the cases. But on another hand, the report underlines the fact that chemical contamination is a very important parameter. Furthermore, the report highlights the fact that if bacteria can be removed by boiling water, it is not the case for dissolved pollutants.

CONCLUSIONS

As we present in this paper, not only in developing but also in developed countries, rainwater harvesting and re-use are contemporary issues. Moreover although the situation in these countries is clearly different, we can see that in both cases problems of pollution emerge. The risks can be chemical by the spread of biocides, or it can by bacteriologic by the development of algae, fungi or bacteria. Consequently, if in developing countries it is important to study the maintenance of the roof and the storage tank, in developed countries, however, an important work has to be carried out to establish the current techniques of rainwater harvesting and to guide the population in case of possible health risks.

Figure 1 :

 1 Figure 1: Roof treatment made by professionals

Figure 2 :

 2 Figure 2: General formula and most known QACs

9th

  World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters: resource or risks? 26-30 October 2009 4 / 5

Table 1 : Listing of the products Product type Number of products Utilisation

 1

	Primary cleaning	3	Primary elimination of plants
	Fungicide	18	Destruction of fungi and incrusted lichens
	Waterproofing	7	Increase of resistance to water for porous material
	Paint	4	Embellishment / Waterproofing

AKNOWLEDGMENTS

This study is financed by Conseil Regional d'Ile de France, in collaboration with Laboratoire Eau, Environnement et Systèmes Urbains (LEESU), Eaux de Paris and Centre Scientifique et Technique du Bâtiment (CSTB).


Marielle Naah
email: marielle.naah@cereve.enpc.fr

Impact of the urban development of the Mingoa River watershed on the Municipal Lake of Yaoundé, Cameroon

Keywords: Contaminants, developing countries, pollutants, wastewater, sediments

Currently, Africa is the less urbanized region in the world. But that trend will change by 2020. Their urban development and globalization have promoted developed countries lifestyle, despite poverty. That means the use of chemicals. Sanitation issues have led to the discharge of untreated wastewater, and as a result, to the emission of persistent pollutants, harmful for human health and for the aquatic environment. Chemicals leading role in economy and in the improvement of life quality has to be weight against their potential negative impacts. The risk represented by these impacts makes chemicals management, an issue of sustainable development. According to a UNEP report, that topic is little documented in Africa. Our work aims at reconstructing an historical link between the urban development of the Mingoa River watershed and the Municipal Lake organic pollution. Thus, we are going to examine the sedimentary compartment using pollutants as tracers. Given that we have not started yet the laboratory work, this article is an introduction to the study.

INTRODUCTION

In African cities, lifestyle has promoted the use of chemicals in all fields. But contrary to developed countries, the management of their impact on the environment, particularly on water resources is not optimal.

African lakes participate in a significant way to the socio-economic development of the region. But they are subject to the demographic pressure, to the urbanization, and to the industrialization. These issues have modified the working of aquatic ecosystems. Thus, lakes are threatened by the lost of their biodiversity, by the enrichment of water, and by chemical contamination. In this work, we present the case of Yaoundé Municipal Lake, in Cameroon.

Urban context of Yaoundé

Yaoundé is characterized by a lawless occupation of space due to the complex procedure to obtain land property. It is very expensive for poor households. In addition, the residential segregation inherited from the colonial period, has been maintained « [START_REF] Wethe | Assainissement des eaux usées et risques socio-sanitaires et environnementaux en zones d'habitat planifié de Yaoundé (Cameroun)[END_REF] ». There are two towns in Yaoundé:

• The organized and administered town represents the previous colonial sites. There we will find residential neighbourhoods, new administrative and commercial shopping centres. These areas have well constructed roads, water supply, sanitation and electricity.

Hardly 40 % of Yaoundé households live in these conditions. • Poor urban settlements are the places were indigenous populations used to live during the colonial period. These areas are suburbs over populated, and located close to industrial areas. There is are no social services like water supply, sanitation and waste management facilities.

Urban context of the Mingoa River watershed

The Mingoa River watershed is located in the centre of Yaoundé, between 3°51'31'' and 3°52'27'' of north latitude and between 11°29'46'' and 11°30'49'' of east longitude. Its relief is steep. It is part of the Mfoundi watershed, the river that drains an important part of the town. Its surface area is 362 ha. In its upstream part, (217.2 ha), there are 12 neighbourhoods and the Municipal Lake. The watershed is drained by the Mingoa River. This one is fed by the Ntap -Ntap source from Melen 4, Commando source from Melen 1, and by its affluent Ntougou from Elig-Effa 7.

The built of a dam on that river at the beginning of the 1950's has led to the Municipal Lake of Yaoundé. For years, the lake has been a leisure place. But since the 1980's, the sanitation infrastructures located upstream are not operating. Thus, untreated water enters the lake continuously. Mingoa River watershed and the Municipal Lake The pollution coming from the upstream part of the watershed is characterized by a continuous discharge of domestic wastewater (baths, emptying toilets, washing, and dishwater). One of the main causes of the pollution is the mal functioning of a wastewater treatment plant located before the lake. The pollution is accentuated by the use of pesticides and by livestock farming (pigs and chickens). That context has led to the contamination of soils, and of groundwater. In addition, it has promoted the proliferation of pollutants like:

• Solids (suspended solids, solid wastes)

• Chemicals ( heavy metals, detergents, solvents, hydrocarbons)

• Microorganisms, viruses, bacteria. It is important to note that among all the studies we have found, the majority is represented by Masters and PhD dissertations.

In our literature review, there was no work on persistent organic contaminants. Thus, our goal is to recreate the historical link between the Municipal Lake pollution and the urban development of the Mingoa River watershed in order to produce data. Therefore, we are going to examine the sedimentary compartment using pollutants as tracers. We have chosen to study PAHs, PCBs, parabens and triclosan. Heavy metals have been added to the list given their daily use in various products.

Because we are just starting the field work, we will not show results in this work. We are going to present:

• The analytical methods of the solid phase by gas and liquid chromatography,

• And the difficulties we have met in Cameroon.

MATERIAL & METHODS

Field study

The physical and chemical properties of the lake are those of small shallow tropical lakes. These lakes have a stable temperature, along the water column. Light intensity, dissolved oxygen, and nutritive elements are modified along the water column. These data are dependent of Yaoundé climate (two rainy and two sunny seasons). ZEBAZE TOGOUET et al., (2004) have established that dissolved oxygen lacks at the bottom of the lake, instead of the permanent saturation of the superficial layers. They have also concluded to the enrichment of the lake by nutrients.

Choice of the studied pollutants

In order to choose the studied pollutants, we have put forward two hypotheses:

• The use of personal and household care products has been more and more important along the years. They contain substances that are not degraded in the environment, particularly in water. They can accumulate in the sediment and become tracers of urbanization and of its pollution. • Urban activities like transport or solid waste burning facilities produce persistent pollutants. We suggest that the restrictions made in developed countries for some chemicals in the 70/80's are not implemented in developing ones, in particular in Cameroon. We think we are able to find these products in the deep layers of the sediment as well as in the superficial ones.

Choice of sampling sites

In order to take a sample of sediment, we are going to locate peaks and troughs. In the context of a temporal study, it is important to keep the order of deposit. The lake bathymetry has made possible the identification of shallow areas. We have used a Garmin GPS during the study, and a software called Surfer in order to process data.

Methods analysis of sediments

The literature review has been made using Science Direct and ISI Web of Knowledge.

RESULTS AND DISCUSSION

Studied pollutants

Parabens and triclosan are among the most used chemicals in personal and household care products. PAHs, PCBs and heavy metals are produced by urban activities like transport and

Bathymetry

The results are presented in figure 4. It suggests that the central part of the lake is the deepest with the point 29.

Actually we are thinking to a sampling method to high depths, without a core drill. Indeed in Cameroon, laboratories are not well equipped for that kind of study. And even if it had been the case, it would not have been possible to rent because the cost is very important.

However, we have tried to do the sampling with a PVC pipe (diameter: 12.5 cm; length: 2.60 m).

Given that the pipes are sold with a 6 meters length, the sampling can be done everywhere in the lake. But there are inconvenient:

• It is very difficult to eliminate the water preceding the sediment in the pipe during the sampling; • It is not easy to reach the sediment layers we need for a temporal analysis given that man strength is not enough when he is working on a pedal boat or on a canoe.

We have sampled at the point 18 (see figure 4). We have only reached the superficial layer. The sample is mud containing plants and trees waste.

After the sampling, the pipe's part containing the mud has been kept at 4°C in a cool box. Then it has been sampled in small glass pill-boxes. We have used a plastic one for the heavy metals analysis. Finally, we have lyophilized the material.

Methods analysis

The literature review has facilitated the building of a method for the analysis of sediments.

CONCLUSIONS

Cameroonian authorities wish to rehabilitate the lake. Thus, the site could be a place of sport and leisure. However, such activities can bring back persistent pollutants in the water column. Given that these chemicals have negative impacts on human health and on the aquatic environment, it is important to pay attention to them. There are no data available regarding their levels in Cameroon. Our study is a good introduction in order to reach that goal, furthermore if we are able to reconstruct a historical link between that pollution of the lake's sediments and the urban development of the Mingoa River watershed.

Figure 1 :

 1 Figure 1: Upstream part of the Mingoa River watershed (Google Earth modified, 2006)

Figure 2 :

 2 Figure 2: Water system of Yaoundé (LESEAU, 2007) There are 21500 inhabitants in the watershed, with 478 inhabitants/ha. There are luxury houses, commercial establishments, schools, slums, hospitals and hostels « TANAWA et al. (2004) ».

9th 10 Figure 3 :

 103 Figure 3: Standing of housing in the upstream part of the Mingoa River watershed (NGIKAM, 2008) Assessment of the Municipal Lake pollution and its management at the watershed level Studies have been made in different fields in order to describe the pollution. Bacteriology has been studied by JUGNIA et al. (1998, 1999, 2001); and by NJINE et al (2001). The impact on aquatic wildlife has been presented by ZEBAZE TOGOUET et al. (2005, 2007); and TADONLEKE et al. (1998). KOUAM (2004) has worked on the vulnerability of the superficial water table against the watershed pollution. WETHE (2003) and TANAWA (2004) have suggested techniques for the management of wastewater. NGIKAM (2007) has studied the public health issue. A study of LEOPOLD (2008) has presented the water pollution by heavy metals.

  Figure 4: Municipal Lake bathymetry

Table 1 : Characteristics data of the Municipal Lake of Yaoundé (Source: NJINE T. et al, 2007)

 1

	Characteristics Altitude	length	Width	Surface area Maximal depth (Zm) Minimal depth
	data	710,8 m 576,5 m 267,5 m	80 000 m	2	4,3	2,4

  These substances are not degraded in the environment and are able to accumulate in sediments. Their log Kow values are presented in table 2.

	9th World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters:
	resource or risks? 26-30 October 2009
	burning waste.
	6 / 10

Table 2 : Log Kow of studied organic pollutants

 2

	HAPs	PCBs	Parabens	Triclosan
	4,79 -8,20	4,3 -8,26	1,96-3,61	4,8-5,4

  protocol analysis has been validated by LEESU on certified samples of PAHs and PCBs. It recommends an extraction with microwaves, and with a mix of CH 2 Cl 2 /MeOH as extraction solvent. Purification of PAHs and PCBs extracts has been made on silica gel. In the literature, the extraction of triclosan using microwaves and different solvents is presented (table3). For the purification step, different stationary phases are used with various elution solvents. Analytical methods for triclosan and parabens are presented in tables 3, 4, 5.

	9th World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters:
		resource or risks? 26-30 October 2009
		Sampling
		Freeze drying
	Heavy metals analysis		Organic products analysis
	Mineralisation	PAHs and PCBs extraction	Parabens extraction	and	triclosan
	ICP-AES or AAS	Purification on silica gel and	Purification on column and
		sulfur	removal	with	sulfur removal with activated
		activated cupper		cupper
		GC/MS			LC/MS
	Figure 5: Methodology for sediment analysis
			8 / 10

A

Table 3 : Analytical methods for triclosan and its derivatives

 3

	Extraction methods	Soxhlet	Pressurised Liquid Extraction (PLE)	Microwaves	Ultrasonication
	Extraction solvent	Ethyl acetate	Acetone	CH 2 Cl 2	acetone/MeOH	Ethyl acetate
	Stationary phase for purification	SPE with silica, and GPC		Silica gel	silica cartridge SPE -Oasis HLB and	Sep Pak C18
	Elution solvent	SPE-ethyl acetate, GPC		CH 2 Cl 2	Ethyl acetate	Ethyl acetate
		-cyclohexane

Table 4 : Analytical methods for triclosan and parabens (Me, Et, Pr, Bu, iPr)

 4

	Extraction methods	Matrix Solid Phase Dispersion (MSPD) Pressurised Liquid Extraction (PLE)
	Extraction solvent	acetonitrile	Ethyl acetate
	Stationary phase for purification	SPE florisil	florisil
	Elution solvent	CH 2 Cl 2	Hexane
	Author	CANOSA P.	CANOSA P.et al. (2007b)
		(2007a).
	Table5 :

Analytical methods for parabens (Me, Et, Pr, Bu, iPr)

	Extraction methods	Ultrasonication
	Extraction solvent	acetonitrile
	Stationary phase for purification
	Elution solvent
	Author	NUNEZ L.et al. (2008.)

/ 10


Juan Pablo
email: jpabdo@yahoo.com.mx

Gómez-Jáuregui Abdó

Domestic freshwater usage under the final user perception. Evaluation of the metropolitan zone of Guadalajara

Keywords: Management, Sustainable development, Social conflicts

Domestic freshwater usage under the final user perception. Evaluation of the metropolitan zone of Guadalajara

INTRODUCTION

Even though the majority of the surface of our planet is in covered by water, only 0,26% of the total water available can be used for human consumption. In relation with the use of freshwater, the agriculture sector used 70% of the available water worldwide, while industry used 20%, and only 10% was used by households [START_REF] Connors R | Water in a changing world[END_REF]. The urban water consumption shows a different picture, while in the national water consumption the agricultural usage represents the majority. In big urban agglomerations the households consume a bigger percentage of the water distributed. In big cities such as Berlin (73%) (Heizmann, 2000), Melbourne (60%) (Melbourne Water, 2009), Barcelona (65%) (Barcelona City Council, 2000) and Mexico City (67%) [START_REF] Soto | Agua: Tarifas, escasez y sustentabilidad en las megaciudades. Cuanto estan dispuesto a pagar los habitantes de la Ciudad de México?[END_REF], more than half of the distributed water is used for domestic consumption purposes.

In 2004 it was laid down in the national water law that at least 50% of the council participants should be users' representatives. However this citizen representation is fragile due to different factors; several parties with different interests are represented, and sometimes these interests are different (like agricultural and domestic needs); also some of the users' representatives are weakly selected because the civic groups are not strong or well consolidated. This fragility impacts in the knowledge of the decisions taken. There are not efficient mechanisms to inform the represented about the decisions made in the council [START_REF] Torregona | Gestión integrada de consejos de cuencaen México. Un proceso en construcción[END_REF]. The major aim of this study is to analyze the householder's perspective about domestic water supply issues in the metropolitan zone of Guadalajara (MZG). The study focuses on some characteristics of users' water consumption; the users' will about water saving; the water supply perception by the final user; and the conflicts related with the water supply and sewage systems; Water consumption per capita is an important variable which is use to determine water consumption demand and allows performing forecasts. However, most of the time, the mean or average value of water consumption per capita is used without looking how water consumption is distributed. If a distribution is positive skeweed, that means more percentage of the users consume less water per capita than the mean; on the other hand, if the distribution is negative skeweed, more users consume more water per capita than the mean. One of the goals of this study is to find the characteristics of the probability distribution of water consumption per capita.

On industrialized countries, such as EU countries, United States or Australia, consuming drinking water directly from the tap is an usual activity. The lack of adequate safe drinking water supplies that still face the less developed countries (ASCE, 1998) pushes towards to a major bottled water consumption. As is stated by several environmental organizations, Mexico is the second biggest consumer of bottled water in the world just surpassed by the United States of America.

The quality of the water supply service must be viewed from different points of view. Therefore it is important to know how the final users perceive the water supply service and the water related problems in order to know their concerns and the directions that public policies should take. Some of the most important factors related with a proper water supply service are water quality, continuity of the service, customer service (attention to complaints), speed and efficiency in the repairs, among others [START_REF] Contreras | Tienen los organismos de agua en México los incentivos para lograr una gestión eficiente de los servicios de agua potable, alcantarillado y saneamiento?[END_REF].

Overview of the area of study

The city of Guadalajara is the second biggest city in Mexico and is the third industrialized city in the country. Guadalajara is the capital city of the state of Jalisco, localized in the western part of Mexico, and situated in an altitude of 1567 m over sea level. The MZG is composed of four districts: Zapopan, Tonala, Tlaquepaque and Guadalajara. However, the currently growing urbanization is occupying an important sector of the district of Tlajomulco de Zuñiga and el Salto (figure1); having a total population of 4,060,531 habitants, a surface of 544,7 square kilometres1 and with an average annual population growth rate2 of 1,8%. Mexico City, Guadalajara, Monterrey and Ciudad Juarez produce more than 50 percent of total Gross Domestic Product (GDP) of Mexico (University of Monterrey, 2009). In 2000, the GDP of Guadalajara was 8,824 USD per capita (Municipality of Guadalajara, 2001). However, there is great social inequality within the city where most wealth is concentrated in a small sector of the population. Only 8% of the families in Guadalajara earn more than 6500 USD per month, while 57,3% of families must live on less than USD 890 per month (Mexican Associations of Marketing Research and Public Opinion Agencies (AMAI), 2005).

The main sources of freshwater supply in the urban zone of Guadalajara are the Chapala lagoon with 5,1 m3 /sec, subterranean wells with 2,4 m 3 /sec, the Elias Gonzalez Chavez dam with 1,1 m 3 /sec and springs with 0,2 m 3 /sec; having a total supply of 8,8 m 3 /sec (SIAPA, August 2008). Of these, the lagoon of Chapala is the most important water supplier for the MZG.

In the MZG around 70% of the water supplied is consumed by the domestic sector 3 . The main water supplier in the city is the Intermunicipal System of Potable Water and Sewage (SIAPA), which supplies 93% of the total water distributed to the MZG, the rest of the water is supplied by each municipality or is water licensed by the National Water Commission (CNA). The water consumption per capita in Guadalajara is around 214 litres per day (lpd), correlates with a production of residual water of 7,89 m 3 /sec (SIAPA, 2008). Almost 94% of the houses have access to tap water and 98,2% have drainage connection (National Institute of Statistics and Geography INEGI, 2005).

MATERIAL & METHODS

The empirical method used in this study was a face to face interview. The primary unit of observation was the house in which mainly the head of the household was interviewed (the mean age of the respondents was 42 years old). A total of 300 houses from a universes of 914,024 houses (INEGI,2005) were surveyed in the MZG. The survey instrument contained both open and closed questions. The questions were designed to obtain information about water use characteristics, the user's will of saving water, the kind of water saving methods used by the final user, and the final user's opinion about the water supply service and his view of water supply related problems, and to define the socio-economical class to which the user belongs. No timing related questions, such as the time the final user spends in water usage activities, were made due to the uncertainty it brings in the analysis of the different timing perception among the users.

The sampling method used for the study was a simple random sampling of clusters. Originally the proponent decided to implement a stratified sampling using four different socio-economic classes in each stratum, using as a base the results from the national population and housing counting from the INEGI; however the variables used by INEGI does not allow differentiation of the middle and the upper socio-economic classes. Each cluster was defined as an area of 0.346 Km2 from the MZG. Inside each cluster five houses were selected by systematic sampling following three main conditions: The starting point of the sampling route was selected randomly; every 13th house was surveyed; and the houses surveyed should correspond with the general socio-economic characteristics observed in the sub-area. The survey was conducted from May 2008 to June 2008 with the help of 12 interviewers.

RESULTS AND DISCUSSION

The validity of the sample size was verified by comparing five variables between the information from the 2005 population and housing counting of INEGI and the survey's results; and comparing the socio-economic distribution obtained by AMAI with the distribution obtained from the survey's results. The variables comparison is shown in the Table 1. The variables inhabitants per house and rooms per inhabitant presented a confidence interval of 97,5% and 90% respectively, and the socio-economical distribution from the survey showed it belonged to the AMAI's socio-economic distribution with a significance level of 5% (α=0,05) and degree of freedom of 34 .

Domestic freshwater usage under the final user perception. Evaluation of the metropolitan zone of Guadalajara -Juan Pablo GOMEZ JAUREGUI ABDO 5 / 11 Water consumption per capita.

The domestic water consumption per capita in the MZG is positively skewed distributed (skewness of 2,04) with an average daily water consumption per capita of 169.23 litres, as shown in Figure 2. According to SIAPA, the governmental body responsible for the water supply of the MZG, the daily water consumption per capita in the MZG are 214 litres, including the 20.34% lost in the distributions, networks, and in the houses water intake. If we remove the amount of water lost in the system from the total reported by SIAPA, the net daily water consumption per capita is 170.47 litres, which is almost the same amount reported by our results. However, 170 litres lpd are still over the 130-140 litres suggested as the amount of water every person should have access to as part of human and civil rights [START_REF] Arrojo | La nueva cultura del agua del siglo XXI[END_REF] and it is also high compared to some other cities considered sustainable such as Barcelona with 116 lpd (Aigües de Barcelona, 2006), Berlin with 115 lpd (Berliner Wasserbetrieb, 2009) or Singapore with 158 lpd (MEWR Singapore, 2009). Our positive skewed distribution reflects that a bigger percentage of the population (around 68%) consumes less than 170 lpd; however, no relation between the amount of water consumption per capita and socio-economical status could be confirmed. Bottled water consumption.

In contradistinction to European behaviour, the Mexican citizens prefer drinking bottled water to drinking directly from the tap. 99% of the households surveyed consume bottled water for drinking purposes; consuming an average of 2.23 litres per capita per day6 but with monthly expenses of 59.3 pesos (4.56 USD 7 ) per person. However, every person pays an average of 26,11 pesos (2 USD) per month for the water supply service, which means more than 200% more is paid for bottled water as for whole water supply service it self. However if the difference between the bottled water and the water service expenses is expressed in cost per litre, then it represents a very big difference: 1 litre of bottled water in 20 litre container costs in average 89 cents out of a peso (6,8 US pennies), and 1 litre supplied by SIAPA costs 0,47 cents out of a peso (0,036 US pennies). The reason why the householders prefer consuming bottled water for drinking purposes is the lack of confidence in the water quality of the water supply service.

Physical characteristics of the houses regarding water consumption.

In this section some of the most important physical characteristics on water consumption found in the houses are presented.

In Mexico, it is common for the governments to implement occasional cuttings in the water service to save water during shortage seasons. However, this kind of measure does not work properly because the majority of the houses have a cistern or water tanks. According to the survey's results, 50,33% of the houses have cistern and water tank; 32,67% only a cistern; 8,67% only a water tank; and only 8,33% neither.

Water saving devices and methods.

In spite on the fact that SIAPA promotes water saving methods and the use of water saving devices, only 53% of the surveyed householders mentioned they use at least one water saving method; the saving methods most frequently mentioned were reusing the water from the washing machine, reusing the mopping water, and reusing water in general. Only 18% of the respondents have at least one water saving device. The main reasons they do no have any device were lack of awareness of such device, lack of money, and lack of interest. The information obtained from the survey reflects the low impact of the campaigns designed by the decision makers. It also shows that is important that the final user be deeply involved in water savings strategies formulated by the decision makers. Perhaps for that reason, the government of the state of Jalisco together with CNA foster communication and education programs to promote the culture of water as one of the strategies of the Hydrological Program of the State of Jalisco 2010-2030.

Householders' perception about the water supply service, water problematic in the MZG, and citizen organization knowledge.

One of the main goals of the survey was to ascertain how users perceive the freshwater supply service and how much they know about water problems in the MZG. The respondents were asked to rank the water supply service from very good to very bad; as shown in the Figure 3, 82% of the respondents ranked the water supply service between good and very good. Because Domestic freshwater usage under the final user perception. Evaluation of the metropolitan zone of Guadalajara -Juan Pablo GOMEZ JAUREGUI ABDO 7 / 11

ranking is dependent on subjectivity and personal view, an open question was made to determine the reason of the given ranking. The householders who ranked the water supply service "good" and "very good" gave as a main reason of their ranking the availability of water; as opposed to those who ranked the water supply service between regular and very bad, who gave as a main reason water scarcity. It is clear that the cultural perception about a good or bad water supply service depends only in the presence or absence of water leaving important aspects such as water quality 8 , wastewater treatment (just 2,7% of the wastewater is treated) or pricing meaningless even though their lack of confidence in the water quality pushes them to buy bottled water [START_REF] Aguirre | El sistema tarifario en la prestación del servicio de agua potable[END_REF]. The respondents were asked if they believe there exists an overall water problem in the city of Guadalajara; 74,33% answered that they indeed believe that there is a water problem, 22% believed that there is no problem and 3,67% did not know (the results do not show any tendency related to the socio-economic class to which each household belongs). About what kind of water problems Guadalajara might have, the respondents' answers are shown the Figure 4. Once again, the respondents related the water problems mainly to the absence of water, although lack of water saving conscience was strongly mentioned. Nevertheless, just 9% of the respondents mentioned water quality as a problem in the MZG, even though the Santiago River (the river which borders the MZG in the east and northeast) is one of the most polluted rivers in Mexico and the water quality in the lagoon of Chapala is poor (Duran and Torres, 2006;Navarro, Lopez and Caire, 2004).

8 The Lerma-Chapala basin is highly deteriorated due to its poor water quality. Also the deterioration in the water quality of Santiago river is due to the use of the river as a drainage system by the industrial settlements located in industrial corridor from Ocotlan to the MZG and the sewage discharges of the MZG, with almost no treatment [START_REF] Vargas R | El proyecto de Arcedianoy los riesgos a la salud: Existen soluciones o el problema avanza? In: El proyecto de Arcediano y el abastecimiento de agua potable de la zona conurbada de Guadalajara[END_REF]Duran and Torres, 2006). Finally, one question asked in the survey was focused on determining the householders' knowledge about civic groups working on water issues and only 6% of the respondents gave a positive answer.

CONCLUSIONS

If Guadalajara wants to become a sustainable city in its water resource management the first step is to reduce the water consumption per capita. In order to accomplish this goal, good coordination between government and society should take place. It is unacceptable that only 50% of the population is concerned about saving water, and is actually implementing actions about it. However, these single actions, such as just reusing water, or placing a block in the WC container to reduce its capacity, are not enough to significantly reduce water consumption. A drastic modification in water use behaviour is necessary, more promoted water saving techniques and water saving devices as well as better public policies should be implemented to reach these goals.

After reaching an acceptable water consumption rate, the next step in the way of reaching sustainability, is to improve water quality, particularly if the water is used for drinking purposes. It is inacceptable, from a human rights point of view, people prefer to buy bottled water (which is much more expensive as the one supplied by SIAPA) because their lack of confidence on water quality supplied by the network. Almost all bottled water consumed in Guadalajara is produced in Guadalajara by transnational companies. Then it can be conclude there is enough clean water to supply the MZG in order to meet population's needs for drinking and cooking purposes of the population.

Civic participation and public opinions should be the foundation on which public policies are planned. Crucial decisions about water management, particularly involving fresh water supply, should not be taken without knowing the final users' opinions, in this case the householders. Nevertheless, it is crucial that the citizens are well informed about the factors and problems, pros and cons related to the governmental water supply system in order to express and enforce their opinions. If there is no pressure from the society to demand a good water supply service and is Domestic freshwater usage under the final user perception. Evaluation of the metropolitan zone of Guadalajara -Juan Pablo GOMEZ JAUREGUI ABDO 9 / 11 only interested in the availability of water without considering the characteristics of a proper water supply service, the decision makers will focus on accomplishing just this demand. The Arcediano project is a clear example of this situation, where the government, concerned only with satisfying the actual water demand, shows a lack of interest in other important factors like river sanitation or sustainable water consumption 9 .

Education is the main tool to raise awareness of the citizens. Civic groups (Non Governmental Organizations (NGOs), religious groups and education centres) and governmental entities usually are responsible for supplying the proper information to increase awareness about water related problems and the actions and activities the householders can take to contribute to the solution of these problems. Nowadays there are civic organizations, NGOs and academic groups working in Guadalajara trying to solve the water problem in the city, but this is not a solitary work. This should have the support of the entire society. However, how is it possible for the society to support these groups if the people are not aware of them? Nor about the goals and actions implemented by each group? Therefore, it is necessary the mission and agenda of these organizations are promoted in a more efficient way. These organizations need to move the society towards sustainability, even more when the government has shown poor interest in doing it.

9th

  World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters: resource or risks? 26-30 October 2009 2 / 11

11 Figure 1 :

 111 Figure 1: The Metropolitan zone of Guadalajara (ITESO, 2009).

Figure 2 :

 2 Figure 2: Daily per capita water consumption distribution. 5 The socio-economical classes presented correspond to the following: Class A/B = Upper class, class C = Middle class, class D = Lower class and class E = Economical class (class in extreme poverty).

Figure 3 :

 3 Figure 3: Ranking of the water supply service.

TABLE 1 : Survey's validation results 5 .

 1

About which water related problematic exists in the city of Guadalajara

	9th World Wide Workshop for Young Environmental Scientists WWW-YES-Brazil-2009: Urban waters:
		resource or risks? 26-30 October 2009
	Opinion about water related problems in
	9%	Guadalajara
	2%		Shortage and cuttings
	5%
			Lack of conscience in water
	6%	37%	using, and water wasting Bad water quality
			Problems with the water
	8%		supply net
			Water shortage in the future
			Demographic and urban grow
	9%
			Floods
	24%		Others
	Figure 4:
		8 / 11

Source:Aguilar A. (2004). Procesos metropolitanos y grandes ciudades. Camara de diputados, UNAM, CONACYT and Porrua.

Elaborated by the Interagency Panel on the basis of the General Census of Population and Housing of 2000, and counts of Population and Housing of 2005; National Population Council (CONAPO).

In 1999 68,84% of the total water supplied to the MZG was consumed by the domestic sector, this calculation included the water supplied by SIAPA and also the water licensed by the CNA.(Boehm, Duran, Sanchez and Torres, 2002).

A Chi-square test was used to test the socio-economical distribution of our survey fits the socio-economical distribution of our universe of study.

This includes just included the bottled water consumed inside the houses, the bottled water bought out side in smaller presentations was not included in this study.