RAINWATER CATCHMENT AND SANITATION SYSTEM OF ARCHITECTURE SCHOOL OF THE UNIVERSITY OF GUADALAJARA

Transcription

1 RAINWATER CATCHMENT AND SANITATION SYSTEM OF ARCHITECTURE SCHOOL OF THE UNIVERSITY OF GUADALAJARA J. Gleason 1, F. Cordova 2, J. García 2, J. Jimenez 2, V. Reynoso 2 1 University of Guadalajara, agleason@cuaad.udg.mx 2 University of Guadalajara Abstract The present paper describes the Rainwater Catchment and Sanitation Projects of the Art, Architecture and Design Center of the University of Guadalajara or CUAAD (Spanish abbreviations). CUAAD belongs to the University of Guadalajara s network and one of its main areas of academic work and investigation, is the relation between urban design and architecture with the environment. In terms of administration and management of the water resources CUAAD has problems such as: infrastructure of supplying and sanitation on the limit of its life utility; inadequate disposition of wastewater which is throw away in the Ravine of Huentitán; it doesn t take advantage of landscaping potential of the location; and lack of planning and incapacity in the hydraulic-sanitation network. The proposal tries to link many aspects in integral way such as: rainwater catchment actions, which can be oriented to the irrigation, the regulation of stormwater overflows by ponds integrated to a landscape proposal; the hydraulic-sanitation infrastructure restoration actions, (correction and renovation of the water supply and drainage networks), and the separation of drainage into stormwater and sanitary system; the removal of the old septic tank grave that at the moment is in use and the implementation of Biodigesters. Zone of Study CUAAD is in Metropolitan Zone of Guadalajara which is the second largest urban zone of Mexico. It is located in the west of Mexico. It belongs to the basin of the Atemajac Valley. CUAAD is in the north where the Huentitán ravines is, and in its inferior part the Santiago River runs and is united to Verde River. The Primavera Forest is in the west where the Colli Hill is. In the south there are three important hills; the Treasure Hill, the Sentry Hill and the Fourth Hill which is the biggest with 1850 meters over of sea level. In the south there a chain of small Hills. The altitude in the edge of the valley is 1500 meters. The valley is flat with a light slope. The area is millions of m 2 and is limited by this chain of hills which are surrounding the valley. Its main axis is in Northwest to Southeast direction with 33 km of length and 22 km from Northeast to Southwest. Nowadays the Metropolitan Zone of Guadalajara has an Average annual rainfall of 862.7mm during rainfall season (May-October), and its volume is almost millions of m 3. The weather is warm during all the year. Layers of sand compose the subsoil and the basalt rock is to 150 meters of depth. The subsoil in general has a satisfactory index of infiltration. This zone includes 4 municipalities: Guadalajara, Zapopan, Tlaquepaque and Tonalá with a population 4.8 million of habitants. There are industry, commerce, universities, and good communications. In this zone is the capital of Jalisco State.

2 Picture 1. CUAAD Picture 2. Classrooms Problematic CUAAD is located in an extension of almost five hectares. Daily 5, 848 students attend the 13 bachelors, seven masters and a doctorate and 582 professors. It is counted on a network of combined sanitary drainage that evacuates black and storm waters to a septic tank which evacuates them to the ravine of Huentitán. The system was constructed more than 30 years. At the moment the system operates of deficient way, since several pipes are obstructed by roots of trees, others are broken allowing the infiltration of residual waters to the subsoil. The pluvial pipes that drain the roofs of the main buildings find covered causing small floods. In different parts as the parking for cars and in the low parts of the university center appear floods. The sanitary system, as we already said, it is combined, and when the precipitation comes the wastewater with the rainwater saturating the pipes and causing the floods and bad scents. Another one of the factors to get worse the problematic is the lack of maintenance of the system. The waste and storm water networks are already in very bad conditions by the deterioration of the time, they are the same ones since the school was constructed. These conditions cause floods and problems in the operation of the sanitary network. The septic tank already has exceeded its capacity, it is bad located because it dismisses bad scents and it spills to the ravine to a flank of where the new building of Research is constructed. Also we are facing problems of infrastructure of supplying on the limit of its life utility; inadequate disposition of wastewater which is throw away in the Ravine of Huentitán; it doesn t take advantage of landscaping potential of the location; and lack of planning and incapacity in the hydraulic-sanitation network.

3 Picture 3. Floods in Parking lots Picture 4. Drainage with roots Technical Proposal The Rainwater Catchment and Sanitation Projects of the Art, Architecture and Design Center of the University of Guadalajara or CUAAD (Spanish abbreviations), which comprises the initiatives of material and environmental improvement which they are carried out with regard to the Institutional Development Plan referred University Center. The CUAAD belongs to the network of the University of Guadalajara and one of its main areas of academic work and investigation, is the relation between urban design and architecture with the environment. The proposal tries to link many aspects in integral way such as: rainwater catchment actions, which can be oriented to the irrigation, the regulation of stormwater overflows by ponds integrated to a landscape proposal; the hydraulic-sanitation infrastructure restoration actions, (correction and renovation of the water supply and drainage networks), and the separation of drainage into stormwater and sanitary system; the removal of the old septic tank grave that at the moment is in use and the implementation of Biodigesters. The results we want are: the rehabilitation of the hydraulic-sanitation networks, the reduction to the minimum of floods, drastic reduction of water consumption destined to irrigation and human uses it means reduce the supply from the municipality water public agency, the generation of an environmental proposal in the CUAAD that links landscape aspects and the reduction of wastewater and stormwater discharges that cause the erosion and contamination of the Ravine of Huentitán; the mainstreaming of the CUAAD at local, national and international level, as a campus oriented to sustainable approach. Water harvesting potential The total amount of water that is received in the form of rainfall over CUAAD area is called the rainwater endowment of that area. Out of this, the amount that can be effectively harvested is called the water harvesting potential. Among the several factors that influence the rainwater harvesting potential of a site, ecoclimatic conditions and the catchment characteristics are considered to be the most important. a. Rainfall Quantity: Rainfall is the most unpredictable variable in the calculation and hence, to determine the potential rainwater supply for a given catchment, reliable rainfall data are required, preferably for a period of at least10 years. Also, it would be far better to use rainfall data from the nearest station with comparable conditions. Pattern: The number of annual rainy days also influences the need and design for rainwater harvesting. The fewer the annual rainy days or longer the dry period, the more the need for rainwater collection in a region. However, if the dry period is too long, big storage tanks would be needed to store rainwater. Hence in such regions, it is more feasible to use rainwater to recharge groundwater aquifers rather than for storage.

4 b. Catchment area characteristics Runoff depends upon the area and type of the catchment over which it falls as well as surface features. All calculations relating to the performance of rainwater catchment systems involve the use of runoff coefficient to account for losses due to spillage, leakage, infiltration, catchment surface wetting and evaporation, which will all contribute to reducing the amount of runoff. (Runoff coefficient for any catchment is the ratio of the volume of water that runs off a surface to the volume of rainfall that falls on the surface). Runoff coefficients for various catchment surfaces at CUAAD we are taking into account the coefficients which are A Water Harvesting Manual for Urban Areas of Centre for Science and Environment at New Delhi, India. 1 c.) Water harvesting potential at CUAAD Based on the above factors the water harvesting potential of a site could be estimated using the formula given below. Water harvesting potential = Rainfall (mm) x Area of catchment x Runoff coefficient For CUAAD we have taken the following numbers in order to compute: Average annual rainfall = 862.7mm Areas of Catchment = There several areas that we will mention in the next step. Runoff coefficient = 0.90 Areas of Catchment Area Volume Average annual Volume Averagemax/month m² m³ m³ Parking , North building , South Building Roof of the tower Library Roof of Escaleras Image and Sound building Talleres , Total 15,740 12, , Table 1. Water harvesting potential at CUAAD 1 Source : Pacey, Arnold and Cullis, Adrian 1989, Rainwater Harvesting: The collection of rainfall and runoff in rural areas, Intermediate Technology Publications, London

5 Wastewater and irrigation demand As we have already said at CUAAD there are 5000 students and 450 professors so: Students = 5000 * 25 liters/student/day = 125,000 liters/student/day Professors = 450 * 100 liters/professor/day = 45,000 liters/professor/day 170,000 liters/person/day In other words 170 m³/person/day or 34,510 m³/person/year. This is the total demand of sanitation service. Also we are taking into account irrigation at CUAAD about so: Irrigation Potential = (150 m³ / day)*(145 effective days of irrigation/ year) = 21,750 m³/year Rainwater and wastewater treated supply As we have already calculated at CUAAD for rainwater supply we have: Volume Average annual = 12, m³ Days when the buildings are used = 203 Available Daily Supply = 12, / 203 = m³/day Per month = 1793 m³/month And for wastewater treated by biodigestor, we are thinking that if the 60% of the population of CUAAD uses the water system per day and we considerate that only 203 days the buildings are used, so we have: Daily Supply = (170 m³/day) * (0.60) = 102 m³/día Annual Supply = (102) * (203) = 20,706m³/año Finally we resume all the calculation in the following table: Demand Supply Services Daily m 3 /day Annual m 3 /year Sources Daily m 3 /day Annual m 3 /year Sanitation ,510 Wastewater ,706 Irrigation ,570 Rainwater 59 12,315 Total ,080 Total ,021 Table 2. Comparative Analysis We have projected many scenarios since this situation: Ideal Scenario (1). If the total population of CUAAD uses the water services it necessary to use 170 m 3 /day in terms of maximum demand. But we also considerate that if it would be

6 used only the 60% of the demand we can get 102 m 3 /day. If we use this 102 plus 59 of rainwater we can obtain 161 m 3 /day against the 320 m 3 /day in terms of maximum usage. Besides, if we use the waste and rain water supply (161 m 3 /day) only f or irrigation (150 m 3 /day) we cover the total of the need and we obtain a surplus (11 m 3 /day), that we can use partly in water services over all on the toilets. As you can see, we can get almost 50% of benefit in terms of the maximum demand (all the people using the water system at the same time), but if the people uses only partly the system (not all the people) we can cover the 64% of the demand. Realistic Scenario (2). The total of amount of rainwater is not possible to catch up. It represents and enormous challenge in terms of economic and space needs for CUAAD administration. So if we can use only the half of rainwater per day (29.5 m 3 /day) plus wastewater (102 m 3 /day), the amount of water to use will be m 3 /day against the irrigation demand (150 m 3 /day), we will not covering the total of the demand but only in 87%. It represent a good ecological benefit. Landscaping The generation of an environmental proposal in the CUAAD that links landscape aspects and the reduction of wastewater and stormwater discharges that cause the erosion and contamination of the Ravine of Huentitán are some of the objectives that we want to reach out. Not only this, the mainstreaming of the CUAAD at local, national and international level, as a campus oriented to sustainable approach. The proposal includes a small lake or pond at the bottom of the Huentitán ravine. This part of CUAAD no is abandoned and very dirty. As we have already said, at the top of the area there is the parking were the floods affects severely the infrastructure and cars. We have planned to conduct the stormwater flow through new pipes with the rainwater from the roofs, to the small lake. This pond works as a regulation and storage system. The runoff comes down to the pond and it will be retained for a moment and then it will run to the ravine. Instead to have the rainwater at the parking it could be at this lake. The capacity of this pond would be limited and it depends on the intensity of rainfall. During the highest intensities the pond will not retain the total runoff. This pond will use to get landscape with some open spaces for studying, reading, and consulting activities for students and professors. The environment at CUAAD will be improved by this integral project. Picture 5. Present Situation

7 Picture 6. Landscape References 1. AGARWAL, Anil A Water Harvesting Manual for Urban areas Case Studies from Delhi and Mumbai. New Delhi. Centre for Science and Environment ARIAS OROZCO S. et al. Ecotecnologías aplicables a la vivienda. México: Centro Universitario de Arte, Arquitectura y Diseño, GLEASON ESPÍNDOLA, J. A. Manual de aprovechamiento de agua pluviales en centros urbanos.guadalajara, Jalisco, México: Colección Modulor Centro Universitario de Arte, Arquitectura y Diseño, RUANO M. Ecourbanismo, Entornos Humanos Sostenibles: 60 proyectos. Barcelona: Gustavo Gili, SALAS ESPÍNDOLA H. El impacto del Ser Humano en el Planeta. México: EDAMEX, 1997.