THE POSSIBLE INTEGRATION OF A GIS BASED METHOLODOLOGY WITH THE EXISTING COMMUNITY RAINWATER HARVESTING PLAN OF HAUZ KHAS APARTMENT, NEW DELHI (INDIA) Shakti Prakash, Y.P. Abrol, Society for Conservation of Nature 40, SFS, Hauz Khas, Aurovindo Marg New Delhi-110016 Email : shaktitiwari@yahoo.com, ypabrol@vsnl.com India s capital, New Delhi, originally located between the Ridge and the river Yamuna, has now sprawled in all directions, without taking into account its hydrological and hydro-geological aspects. It has been experiencing a severe water crisis for the last several decades or so as against the requirements of 775 MGD of water, it is getting 640 MGD every day. In terms of consumption of water, 93% domestic consumers consume 86% of water, commercial consumers those are just 6% consume 10% of water and 1% industrial consume 4% of water, i.e. 660 MGD or 2996 MLD. This demand & supply gap is a harsh reality in almost in the entire urban spatial entities of the capital, Hauz Khas apartments located at Sri Aurovindo Marg; New Delhi is not an exception A gradual decline in groundwater has been reported in the apartment for the last several years along with scanty municipal water supply. Rainwater harvesting is the best option to augment not only the supply but also the appropriate and sustainable recharge to groundwater level. The present paper proposes the development and integration of a GIS based methodology with existing community rainwater harvesting planning including cost estimates for the construction of 14 recharge wells, plan layouts for diverting stormwater to recharge wells, precautionary measures to be taken to ensure good water quality along with specifications of civil works involved for rainwater harvesting in the apartment which falls in a sedimentary terrain with alternating layers of clay, clayey sand and sandy clay. The total rainwater harvesting potential inside the apartment from different catchments [(rooftop, paved areas & roads, unpaved (parks & open spaces)] has been estimated as 18,986.8 cubic meters. It is estimated that the rain water harvesting and recycling within the apartment would totally eliminate the existing demand-supply gap by the year 2021 as Delhi's endowment of rainwater is about 611 mm of rain per year with a total land area of 1,486 sq km which means ongoing water scarcity can be minimized even with 50 per cent efficiency of the rainwater harvesting systems. Keywords: Rainwater harvesting, GIS based methodology, recharge well, stormwater, bivariate categorical comparison
INTRODUCTION The apartment is located near to Indian Oil Building on Aurbindo Marg New Delhi. The colony gets its water through municipal supply coupled with onsite bore wells. The study area falls in a sedimentary terrain with alternating layers of clay, clayey sand and sandy clay. The groundwater levels in the colony are recorded around 27 metres below ground level (bgl). There has been a rapid decline in the water table in the colony in recent years. There is a critical call for augmenting the depleting groundwater resources. Annually, 1, 89,86,800 lakh litres rainwater can be harvested from the colony. The rainwater harvesting potential of the apartment is shown in the table 1 below: Table 1: Rainwater Harvesting Potential Of Hauz Khas Apartment Type of Catchments Approximate area of the Annual catchments ( Square meters) harvesting Rooftop 16,500 8569.2 Paved areas and roads 16,000 6843.2 Unpaved ( parks and open spaces ) 19,500 3574.3 Total rainwater harvesting potential of the site = 18, 986.8 Cubic meters water Formula Applied for the Calculation of Rainwater Harvesting Potential: Area (sq.km) Annual Rainfall (m) x Runoff coefficient Parameters for calculation: 1. The average annual rainfall in Delhi = 611 mm 2. The peak hourly discharge = 90 mm 3. Sq.1ll stands for square metres: cu.m for cubic metres; mm for millimetres; m for meters and I tor litres. 4. Rooftop brick tiled \\'jth cement coat (runoff coefficient 0.85) 5. Paved area and roads (runoff coefficient 0.70) 6. Unpaved area (runoff coefficient 0.30) THE EXISTING RAIN WATER HARVESTING SCHEME Rooftop water wm the buildings and surface runoff from paved and, unpaved generated during the monsoon are collected in the storm water drain. The open storm water drain runs parallel to the side of the road. The drains are finally connected to the main' drain on western side of the apartment. This rainwater from the storm drains can be effectively used for rainwater harvesting. The rainwater will be basically diverted into recharge wells, which can be located at strategic locations in entire colony. During the site visit it was found that the colony has the open storm water drains near the houses and covered on the internal roads of the co/any. Since the storm water drain is open and not cleaned for long time. Lot of waste materials have accumulated in the drains. So before, implementing rainwater harvesting in the colony, the storm water drains must he cleaned completely.
Another important thing noticed during the visit is that most of the residents have put their washing machines in the balcony and diverted the soap water into the storm water drain in place of sewage as per their convenience. If this soap water is used for recharging purpose directly, it will pollute the underground aquifer and will lead to water quality problem in the area in the near future. To avoid such conditions from ignorance or knowingly. ail such connections, that carry. Soap water or other contaminated water (from bathroom or kitchen) to the storm water drains have to be cut-off and directed to the sewage immediately. They should be maintained after implementation of water harvesting structures also Diversion of Stormwater to Recharge Well : The storm water will be diverted to a recharge well through a 6 inch pvc pipe to a collection cum Filtering tank. The Filtering tank will be O.6m x O.6m x O.6m in size with unpaved bottom as shown in the figure 1. It will be located in the area between the storm drain and road. Storm drain Flow direction Inlet pipe Fittering Tank Interconnection pipe Over flow pipe Recharge well Figure 1: DIVERSION SCHEME OF STORMWATER TO RECHARGE WELL The desilted water then will be diverted to recharge well of 1.5 1.5 2 m in size. The recharge well has a recharge bore well 150 mm diameter and 18 m depth (from ground floor). The recharge bore well will be drilled with hand bore set. The casting pipe of the recharge well will be of 6-inch diameter PVC pipe. The bottom portion of the casting pipe in the recharge well up to 0.6 will be slotted. The slots will be of 15-20 mm in dia and be closely wrapped with jute coir. This will prevent the entry of fine silt to the recharge bore. The recharge well will be filled with layer of filtering materials. A layer of pebble of 0.5 would be overlained by another layer of coarse sand of 0.3 thicknesses The recharge well and the desilting tanks will be covered by RCC slab. The recharge well also be provided with arrangements for over flow. The details of recharge well are shown in the figure 2:
Diversion of Rainwater T Recharge Well Interconnection pipe Manhole Air vent RCC Slab Overflow pipe to storm water drain Fittering Tank Stone slab Brick wall (230 mm) PCC footing Recharge bore (150 mm dia) Slotted casing with coir wraping Figure 2: Detailed schematics of recharge well The entire cost involved in the construction of recharge well is Rs. 15,668.00. Cost details of other components are given in the table 2. The actual cost of recharge well is Rs. 15,668.00 and number of such well required in the apartment is 14. TABLE 2: Cost Estimates for recharge Well Sr. No Item work Quantity Unit Rate ( Rs) Amount ( Rs) 1 Filtering tank (0.6 0.6 0.6 m) 1 No.s LS 800.00 2 Recharge well Excavation 6.46 Cu.m 90.00 581.00 PCC 0.22 Cu.m 2700.00 594.00 0.23 m thick brick lining 2.02 Cu.m 1300.00 2626.00 100 mm thick RCC slab ( 1 :2:4) 0.242 Cu.m 4700.00 1137.00 3 In well bore M Drilling of 150 mm bore hole 17 M 250.00 4250.00 Plain Casing pipe ( PVC) 6 inch.6 kg/cm 2 17 M 230.00 3910.00 Brickbat Pebbles, Slotted pipe and coir packing L.S. 1500.00 Inter comnections pipe 1.5 M 180.00 270.00 Total cost : Rs. 15, 668.00 Diversion of Stormwater to Recharge Well Through Desilting Chamber : There exists the main storm water drain in the lawn near to main road. The rainwater from this drain will be diverted to a desilting chamber through a 6-inch pvc pipe. The desilting chamber will be of 1m 1m 1m in size with unpaved bottom. This will ensure the settling down of the silt and suspended materials in the storm water. The desilted water then will be diverted to recharge well of 1.5 m 1.5 m 2m in size. The recharge well has a recharge bore well 150 mm diameter and
18 m depth (from ground level). The recharge bore well will be drilled with hand bore set. The Casing pipe of the recharge well will be of 6-inch diameter PVC pipe. The bottom portion of the casing pipe in the recharge well up to 0.6 m will be slotted. The slots will be of 15-20 mm in dia and be closely wrapped with jute coir. This will prevent the entry of fine silt to the recharge bore. The recharge well will be filled with layer of filtering materials. Another layer of coarse sand of 0.3 thicknesses would overlie a layer of pebble of 9.5. The recharge well and the desilting tanks will be covered by RCC slab and manhole will be provided for cleaning purposes. The recharge well will also be provided with arrangements for over flow. The details of recharge well are given in the figure 3. Cross section of the Recharge well Inlet from storm drain Storm water drain Inlet from desilting chamber Air vent Manhole RCC Slab Overflow pipe to storm water drain Brick wall (230 mm) Desilting chamber Stone slab Coarse sano Peabbles PCC footing Recharge well Recharge bore (150 mm dia) Slotted casing with coir wraping Figure 3 : Cross section of recharge well The total cost of implementation of recharge structures in the apartment is: Rs. 2, 36,261.00. Cost estimates for other components are given in the table 3: Table 3 : Cost Estimates for Constructing Recharge Well with desilting Chamber Sen Item of work Quantity Unit Rate (Rs) Amonut ( Rs) 1 Desilting Chamber Excavation 4 Cu.m 90.00 360.00 Brick work 0.92 Cu. m 1300.00 1196.00 RCC Slab of 100 thick 0.1 Cu.m 4700.00 470.00 2 Recharge Well Excavation 12.5 Cu.m 90.00 1125.00 PCC 0.3 Cu.m 2700.00 810.00 0.23 m thick brick lining 2.76 Cu.m 1300.00 3588.00 100 mm thick RCC slab ( 1:2:4) 0.4 Cu.m 4700.00 1880.00 Drilling ( 6 inch bore using hand bore set) 16 16 M 250.00 4250.00 m bore from the bottom of the recharge well 6 inch PVC casting pipe 17 M 230.00 3910.00 Brickbats Pebbles, sand and coir packing L.S 1200.00 Total cost Rs. 16,909.00
Associated Precautionary Measures: I. There should no contamination in around areas contributing to catchments. II. There should regular cleaning of areas contributing to catchments. III. Storm water drain should be cleaned before the onset of monsoon. IV. Use of pesticides and insecticides must be avoided. V. There should be periodic monitpring of all rainwater harvesting structures. THE PROPOSED GIS BASED METHODOLOGY The existing rainwater-harvesting scheme stresses more on construction of RWH structures without any attention to household level characteristics along with existing and future demand and consumption patterns Demand control policies, however, require that water supply agencies (DJB) should establish complete accurate and representative information about current water consumption patterns. A realistic assessment of water consumption is essential in understanding how water suppliers can accommodate variations in time and type of use. Consumption patterns include a number of water use characteristics representative of the individual users in space and time. These characteristics include, but are not limited to: the number of inhabitants to be supplied with water and their demographics; the consumption habits of the population; the type of development, apartment size; and associated landscape. Each of these (and several other) parameters play a role in explaining overall demand. However data limitation has precluded analysis of the effects that these variables play. So far MCD, DJB etc have relied upon analysis of large-scale consumption patterns to evaluate management options. There is an urgent need today to understand better the general patterns associated to water use in the supply region. Once identified, water suppliers can curtail demand by evaluating alternative demand-oriented management options tailored specifically to those areas. There is an urgent need to develop a GIS based methodology upon which householder characteristics can later be incorporated. Moreover, GIS based approach will be the unique piece of the rainwater catchments assessment, namely, the identification of households within specified areas with highest potential for water conservation. The developed methodology will use Geographic Information System (GIS) and empirical data for analyzing spatial water consumption patterns with the objective of prioritizing water conservation areas within the apartment, The GIS analysis to be used for the apartment is essential to evaluate systematically the potential for installing rainwater-harvesting systems within the apartment. The ability to overlay large varied datasets, and code for specific representations proved easy and effective. In fact, due to readily available geocoded data for the apartment, it will be possible to complete the development and integration of GIS based methodology in a timely and efficient manner. Through GIS analysis the apartment will able to prioritize residences that could potentially be candidates for installation of such systems. Clearly, some assumptions will be needed to be examined in greater detail when installation of a system is to occur. For example, we are comfortable with the assumptions of homogenous water demand, equal irrigation rates for parks and total rainfall capture at the apartment scale; however, at this point it is impossible to know if the specific residence of interest is able to accommodate the installation of a rainwater harvesting system. There are many instances where landscaping or configuration of underground piping/wiring may prevent such installation. Therefore, it is recommended to opt for ground-truthing all residences of interest and evaluating the area for any circumstances not captured in this analysis. With the success of applying this methodology to the ten priority residences, it is expected to perform this analysis to the entire apartment in the near future. As such, we expect to identify all sites with high conservation potential and use the GIS to present the findings to apartment officials. With limited
resources to be spent on innovative project at the apartment scale, this methodology will enable us to identify specific residences where investments can occur. The next phase of the development and integration of GIS based methodology will be to examine the fiscal implications of installing these systems on selected residences, and the willingness-to-pay of those households selected. The major steps involved in the complete development of the proposed methodology discussed in the aforegoing paragraphs will be: 1. Residence / (or plot) based analysis of water use for Single Family Residents (SFR) 2. Recognition of the seasonal variation in water consumption 3. A bivariate categorical comparison between the built area and no built area of each priority residence. 4. Identification of all residences with the highest percentage of comparable built versus nonbuilt areas. 5. Use of only those residences with the highest conservation potential with building area and historic rainfall data to calculate potential for water capture for the ten priority residences. By averaging rainfall data over the last 57 (1945-2005) years during summer/winter months, we calculate total runoff volumes from all SFR buildings in the ten selected priority residences The rainwater capture from those residences having highest conservation potential will enable us to estimate the amount of water to be removed from the drainage system. A standardized geospatial database will be central in the proposed GIS based methodology. It will enable us - data once incorporated in a GIS form- to link up a variety of information simply having one common ID (like e.g. neighbourhood ID, Name ID, Grid ID, etc), which can then be visualized in a map. GIS will allow us to work with spatial as well as non-spatial information at the same time. Display of thematic and street-based mapping systems along with the ability to analyze geographic locations and the information linked to those locations is combined. It is also dynamic, as updated information is linked up which automatically reflect those changes. Maps for presentations have been easily created. This tool will allow apartment to visualize and analyze information in a more open and easy manner. Moreover the water level and quality parameters vis-à-vis seasonal changes are also being monitored, which helps us visualize ground water status and model the same for predictions Conclusions It is very well known that water demand indicates both current and/or expected water consumption in any given area over a specific time period. Due to varying requirements and spatially explicit characteristics of individual users, water demand must be determined separately for individual user groups. Residential settlements with over 150 residents as well as several construction sites, neighbourhoods, buildings, water tanks etc can be surveyed. Hauz Khas apartment as well as several other construction sites, neighbourhoods, buildings, water tanks etc can be surveyed and will be integrated and accessible in GIS. Water consumption patterns can be monitored and e.g. with the help of GIS the data can be quickly assessed and compared. An unusual high consumption can be easily visualized (maybe a leaking pipe, over consumption by residents etc) and appropriate measurements can be taken and will be accessible in GIS based proposed methodology. Water consumption patterns can be monitored and e.g. with the help of GIS the data can be quickly assessed and compared. An unusual high consumption can be easily visualized (maybe a leaking pipe, over consumption by residents etc) and appropriate measurements can be taken. The integrating the existing community rainwater harvesting planning for Hauz Khas apartment, New Delhi (India) into the proposed GIS based methodology will enable inhabitants in efficient and sustainable rainwater harvesting in side the apartment.