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1 Conferencia Internacional Usos Múltiples del Agua: Para la Vida y el Desarrollo Sostenible,17(*5$7('0$1$*(0(172)*5281':$7(55(6285&(6 6867$,1$%,/,7<,17+($48,)(5(;3/2,17$7,21,1(63(5$1=$&,7< $5*(17,1$ 7XMFKQHLGHU2 3DULV0 3pUH]0 \' (OtD0 &RQVHMR1DFLRQDOGH,QYHVWLJDFLRQHV&LHQWtILFDV\7pFQLFDV&21,&(7 pichy@fich.unl.edu.ar )DFXOWDGGH,QJHQLHUtD\&LHQFLDV+tGULFDV8QLYHUVLGDG1DFLRQDOGHO/LWRUDO),&+81/ &DVLOODGH&RUUHR6DQWD)H±$UJHQWLQD7()$;±H[W mparis@fich1.unl.edu.ar; maperez@fich.unl.edu.ar; mdelia@fich.unl.edu.ar $%675$&7 Nowadays, groundwaters constitute the only supplying source for Esperanza and Rafaela cities (Santa Fe, Argentina). The main economical support of the regional social system is offered by the agriculture, cattle and a varied industrial activity, which permanently act over the aquifer system modifying both its quali and quantitative characteristics. In this context, the preservation of the groundwater resource constitutes a prime objective, which must be founded in the integrated knowledge of the environmental system. With this cognitive framework, the implementation and validation of methodologies -to outline future exploitation scenarios and to appraize properly the system response capacity-, allow the development of tools those contribute in the definition of integrated management guidelines of the groundwater resources in order to guarantee the exploitation sustainability. The results obtained by the integrated management model of the groundwater resources proposed for Esperanza city are presented here. This includes: aquifer pollution vulnerability evaluation, contaminant load characterization, demand quantification, hydrogeologic mathematical modelling, well head protection areas, exploitation schedules, definition and operation of the monitoring network.,1752'8&&,21 Esperanza city (Provincia de Santa Fe, República Argentina) has an area of 276 km 2 and 35,000 inhabitants (Figure 1). Its sanitary infrastructure covers about 40% with sewer and 70% water supply system in the urban area. The water mains comprise 8 wells for Esperanza city and 14 wells for Rafaela city, all of them placed in Esperanza district. The average well deph and withdrawal are 45m and 75hm 3 /h (1,800m 3 /day), respectively. The production is about 15hm 3 /year, but it does not include the private extraction volumes (5hm 3 /year) that are related to industrial and agricultural activities. Since 1997 Esperanza city is target of research by Grupo de Investigaciones Geohidrológicas (GIG) of the Facultad de Ingeniería y Ciencias Hídricas (Universidad Nacional del Litoral). Their results have allowed to determine the main quali-quantitative characteristics of the hydrogeological system as well as socio-economical aspects of this region and to define some strategies to protect the resource (Tujchneider HW DO., 1998; Paris, HW DO., 1998a, 1998b, 1999; Tujchneider HW DO., 2000). These are: wells relocating outside the urban activities influence that can produce pollution hazard (Paris HWDO., 1999), wellfield design according to both local hydrogeological characteristics (better in the rural area), borehole quantity, distance and operation schedule (increasing the number of the wells to decrease the unit withdrawals-lower than 60m 3 /h with 500m as a minimun distance) (Tujchneider HWDO., 2000) (Figure 2). Universidad del Valle/Instituto Cinara Tujchneider, O., HWDO. 205

2 Figure 1. Esperanza city, Provincia de Santa Fe, República Argentina. Localization. Figure 2 Localization of perforations Esperanza is placed in the Chaco-Pampeana plain that is defined with low slopes in land surface where fresh water reservoirs are corresponded with geomorphological particular aspects that allow meteoric water infiltrates and stores. Annual mean precipitation is 930mm and the real mean evapotranspitarion estimated by Thornthwaite-Matter method is 890mm. So, the mean excess is 40mm/year of which 28mm/year have the possibility to recharge the aquifer according to the mean water balance results ( period). Universidad del Valle/Instituto Cinara Tujchneider, O., HWDO. 206

3 Soils are argiudol type with a B 2 t horizon with 60% of expansible clays. This condiction can impede the infiltration although its expansible property can produce fissures as a preferential way to penetrate in the subsoil during dry periods. In deep, hydrogeological systems have a multiunit behavior with very complex hydraulic relations. The exploitation aquifer is semi-confined, with a mean thick of 24m and it is lodged into Puelche Formation sands. Besides, this aquifer maintains hydraulic relation with an un-confined one whose yield is low and it is up-lodged into tills and clays of Pampa Formation. Between of them, there is an uncontinuous clay strate in some places (average thick 3m) with an aquitard hydraulical behaviour where vertical flows through up and down are produced. The general groundwater flow direction is West-East and its hydraulic gradient is 2*10-4. Puelches sand aquifer transmissivity is about 600m 2 /d. and hydraulic conductivity 25m/d. As long as supply requirements of both population, the need to guarantee the economical activities development and besides the aquifer protection, the purpose of this work is the planning and performing an integrated management model of groundwater resources. 0(7+2'2/2*< The natural and the social-economic-cultural systems were analized together with the diagnosis of the environmental system with a global point of view. In order to propose actions that allow the improvement of the groundwater supply control and management, this environmental system is considered as the conceptual basis. The social and economical system was characterized taking into account the information came from the Instituto Provincial de Estadística y Censo of the Santa Fe province. The Centro Industrial, Comercial y Afincados de la Ciudad de Esperanza (CICAE) of Esperanza city provided the industries inventory in which their location and type were presented. On the other hand, the amount of the different types of industries was obtained from the Dirección de Planeamiento of the Esperanza Municipality. The aquifer vulnerability was determined using the GOD methodology (Foster & Hirata, 1991). For this, information related to stratigraphic profiles and water levels since 1994 to 2001 from 20 wells was considered. Aquifer hydraulic parameters were calculated from pumping tests that were done in the area. A hydrogeologic mathematical model was implemented based on the conceptual model previously defined (Tujchneider HW DO., 1998 and 2000) in order to study the system evolution. Visual ModFlow v code (Guiguer N. & T. Franz, 1998) was used. The area was discretized into 200, 250, 500m of sides rectangular areas and the aquifer was considered divided into three layers: an unconfined aquifer ( 3DPSDFormation ), a semiconfined layer and a confined aquifer ( 3XHOFKH Formation ). The thickness of each layers were obtained from the analysis of the well profiles in the area. The hydrogeological parameters (hydraulic conductivity, porosity and storage coefficient) were considered as constant ones in the whole area taking into account the values calculated from the pumping tests mentioned above. The recharge amount considered in steady state was 28 mm/year and was calculated as an average of the monthly estimated recharge from period. Monthly estimated recharge was considered in the transient state simulation (Paris HWDO., 2002). The ModPath module was used to delineate the capture zones in the well field. The flowpath of the particles was defined in a given time considering the steady state simulation outputs obtained from Universidad del Valle/Instituto Cinara Tujchneider, O., HWDO. 207

4 3D model ModFlow. It is important to note that the well field was designed to supply groundwater to Esperanza and Rafaela cities according to a given withdrawal scheme. An advective transport regime in the aquifer system was considered in a forward and backward route direction. 5(68/76$1'',6&866,21 Esperanza economy is supported by a varied agricultural and industrial activity. The more important industrial facilities are located in the urban area. There are 270 farms that cover 19,000ha which more than 9,000ha are used for grazing. The remaining ones are used for growing and suffer modifications depending on the rotation crops system that is related to the market demand. On the basis of local hydrostratigraphic, piezometric and soil characteristics, aquifer pollution vulnerability is moderate (by using GOD index, Foster HWDO., 2002). This appraisal is representative of the general average conditions in the Esperanza district. Taking into account the conceptual model previoulsly defined (Tujchneider HWDO., 1998 y 2000), the mathematical hydrogeological modelling was calibrate by using field measurements obtained in March 1999 and the simulation results were validated with a new data set in December The mean absolute error was 0.78m and the porcentual root mean squared error (SRMS) was 8.80% (Paris HWDO, 2002). The Figure 3 shows the modelling results. (a) Figure 3. (a) Modelling levels, March (b) Simulated levels, December Approximated scale: 1:300,000 (b) The tested exploitation scenes have given different management alternatives for 20 year of demand projection. The integrated analysis allows assessing the modifications that would be produced. The hydrodynamical stage does not present hazard situations to preserve the resources in all of the cases. It is due to the vertical and horizontal flows that are in equilibrium with this water extraction scheme, taking into account average climatic conditions without extreme events. So, the aquifer system can satisfy the present and future demand while the exploitation is done according to the management defined in this integrated model. The permanent system monitoring under exploitation, which is designed on the basis of the hydrogeological context knowledge, has allowed to: assess the variables and relations that define the performance system, identificate critical situations, estimate the time needed to carry out prevented and/or correctived measurements as taking out of service those wells with elevated nitrate concentrations mainly in areas without sewer, operational problems in the wellhead- and/or increasing salinity shows by the total dissolved solid, clorure and sulfate (Figure 4). Universidad del Valle/Instituto Cinara Tujchneider, O., HWDO. 208

5 ;:9 8 5/ 0- /.- Conferencia Internacional Usos Múltiples del Agua: Para la Vida y el Desarrollo Sostenible! #" " $ % & ' ( ) * ( / 2800, , , , ,00 800,00 400,00 0,00 01/03/90 01/09/90 01/03/91 01/09/91 01/03/92 01/09/92 01/03/93 01/09/93 01/03/94 + (, TDS Cl SO4 01/09/94 01/03/95 01/09/95 01/03/96 01/09/96 01/03/97 01/09/97 (a) (b) Figure 4. Evolution of chemicals contends. (a) sec waste, chloride y sulphates; (b) nitrates 135,00 120,00 105,00 90,00 75,00 60,00 45,00 30,00 15,00 0,00 01/02/90 01/02/91 01/02/92 01/02/93 01/02/94 01/02/95 01/02/96 01/02/97 01/02/98 01/02/99 01/02/00 01/02/01 01/02/02 e3 e5 e6 e7 e11 e12 e13 e16 e17 01/02/03 The spatial delineation of the groundwater supply capture zones is presented in Figure 5. In this case, simulation results show that the SDPSHDQRsediments -above SXHOFKHVsands-, would delay the contaminants arrivals to the supply sources. This situation is only produce if the contaminant load is applied on land surface. (a) (b) Figure 5 (a) 3D-model capture area. Contaminant load applied on land surface (b) 2D-model capture area. Contaminant load applied in the aquifer &21&/86,21 According to the obtained results and the advance carried out in the implementation of the groundwater resource integrated management model, it is considered that: Continuing rigorously the system monitoring at real time is of prime importance. With regard to the results of the mathematical modelling and the particle tracking, a maximum time interval of two months is properly considered for controlling the pumping field. The wellhead protection zones must be established on the basis of the capture areas defined for the pumping field, taking into account the type of activities developed in the area. For this purpose, technical and legal guidelines must be established in order to guarantee the effectiveness of these wellhead protection areas and regulate the private withdrawal. Universidad del Valle/Instituto Cinara Tujchneider, O., HWDO. 209

6 It is very important to guarantee the specific prohibition of doing all type of burials and/or injections, especially in depth, because in this case the contaminant flow time is significantly reduced. It must be generated articulated actions with the community in order to achieve a progressive and responsible participation of all the social actors involved. It should be considered the use of surface waters together with groundwaters as a medium and long-term alternative that supplies the region requirements. In order to maintain the environmental system dynamic equilibrium, previously it is neccesary to assess the changes that the new water contributions would generate. 5()(5(1&(6 Guiguer Nilson & Thomas Franz, (1998). Visual Modflow, User s manual. Waterloo hydrogeologic. Foster S., Hirata R., D. Gomes, M. D Elía & M. Paris Groundwater Quality Protection A guide for water utilities, municipal authorities and environment agencies. The World Bank. ISBN p. Paris, M., Tujchneider, O., Perez, M., D Elia, M. & Fili, M. (1998a). El conocimiento del sistema hidrogeológico y desarrollo sustentable de una región. Área de Caso: Ciudad de Esperanza (Provincia de Santa Fe República Argentina). Actas del Simposio sobre Planificación, gestión y economía de los Recursos Hídricos, pp Paris, M., Tujchneider, O., D Elia, M., Perez, M. & Fili, M.. (1998b). Estudio de la interacción entre el sistema hídrico subterráneo y las actividades industriales de la ciudad de Esperanza (Provincia de Santa Fe, Argentina). Primera fase. Anales del XVII Congreso Nacional del Agua y 2º Simposio de Recursos Hídricos del Cono Sur. Santa Fe, Argentina, agosto 3 al 7 de Tomo 3, pp ISBN X. Paris M.; O. Tujchneider; M. D Elia & M. Perez. (1999). Hidrogeología Urbana: Protección de pozos de abastecimiento en la gestión de los recursos hídricos subterráneos. Hidrología Subterránea. Serie Correlación Geológica (13): ISBN Paris, Marta, Mónica D Elía, Marcela Perez & Ofelia Tujchneider. (2002). Análisis estocástico de las variables hidrometeorologicas para la estimación de la recarga de acuíferos. XXXII IAH & VI ALHSUD Congreso. Mar del Plata, Argentina, 21 al 25 de octubre de Libro de Resúmenes y CD Rom. ISBN pp Tujchneider, O., Paris, M., Fili, M., D Elia & M., Perez, M., (1998). Protección de las aguas subterráneas. Caso de estudio: Ciudad de Esperanza (República Argentina). Primera Fase: Diagnóstico del sistema. Memorias IV Congreso Latinoamericano de Hidrología Subterránea, Volumen 2, pp Tujchneider O.; M. Paris; M. D Elia; M. Perez & M. Fili. Modelo de gestión de los recursos hídricos subterráneos en el centro-oeste de la Provincia de Santa Fe-Argentina. I Congreso Mundial Integrado de Aguas Subterráneas. Fortaleza, Brasil, agosto del pp. 138 y 139 Libro de Resúmenes y CD-Rom. Universidad del Valle/Instituto Cinara Tujchneider, O., HWDO. 210