Rainwater Harvesting in Kathmandu ValleyKanchan Mani Dixit Research Associate Nepal Water Conservation Foundation Email: kanchan@ntc.net.np

AbstractRainwater collection is catching rain as it falls. The idea of Rainwater collection however is not new, the evidences have shown that it has been practised since pre-historic times. In Nepal, the first modern rainwater collection system were built during the 1960s. At that time the idea of collecting rainwater couldnot gain popularity as there were abundant availability of water, however with the scarcity of water it is heavily practised today in urban and suburban areas of Nepal. In this paper I have attempted to show the scanario of water scarcity of Kathmandu Valley and discussed the alternatives to the municipal supply. My attempt has been to show that in the Kathmandu Valley, rainwater harvesting is only the best way to fullfull the need than any other available alternatives explained below.

PreambleRainwater harvesting is a system based on collecting rainwater that falls on an impermeable surface and utilize later to meet the diverse requirement of people. It is the art of catching the water drops where they fall before they drain away or escape. The idea of rainwater harvesting, however, is not new. There is an evidence of water harvesting structures since pre historic times. During those times, rainwater was harvested to meet the irrigation water needs rather than for drinking. Ponds, lakes and other storage structures also had been built to capture falling rain and use it later. Greece and Palestine collect rainwater in cisterns, made of rocks, from rooftops and paved spaces during the early periods (Agrawal and Narain, 1997). By the middle of first century, there is evidence that cistern with storage volume of up to 75000 m 3 had been used. In Nepal too, rainwater was collected and used since ancient times. In the hills, people collect rainwater using bamboo slices to meet their drinking water need. In most cases, the water collected has been used for cleaning, washing and irrigation. Similarly, community ponds have been built to collect rainwater and used by a community for washing and cleaning. Rainwater is also collected for the recreational purposes. Rainwater can be collected both at domestic and community level. There were no such scientific structures for rainwater collection until 1960s when rainwater collection was first scientifically tested at Pokhara Hospital (Dixit, 2002). Similarly, the mission hospital in Tansen, Palpa constructed a Rain Water Harvesting System (RWHS) in 1960s, which is still functioning today (Sainju et al., 2000). The concept, however, could not gain popularity at the time because of abundant availability of water. With shortage of potable fresh water, people started to collect rainwater for their domestic and industrial uses. In the rural Nepal, initial effort to collect rainwater at household level was done by FINNIDA in Palpa and Gulmi districts. Since then Department of Water Supply and Sewerage (DWSS), Peace Corps Nepal, Nepal Water For Health (NEWAH), International Center for Mountain Resource Development (ICIMOD), Canadian International Development Agency (CIDA), Nepal Water Conservation Foundation

(NWCF), and Department of Soil Conservation and Watershed Management (DSCWM) have been promoting the system in different districts of Nepal. The harvested rainwater is also used to recharge underground aquifer. People of Rajastan at Alwar collect rainwater in a pond to recharge underground water and as well as meet their daily demand like washing and cleaning. The stored rainwater maintains soil moisture as well as recharge underground water table. In Nepal, there are numerous ponds, which served as a water storage tank. The stored water is used during the dry periods. With the ongoing scarcity of both surface and groundwater, the popularity of community ponds is increasing. The ponds dug in Southern Lalitpur by Department of Soil Conservation and Watershed Management is an example. Similarly, many of such ponds have been built in the catchment of Bagmati River at the foothills of Shivapuri (Dixit, 2002). Nepal Water Conservation Foundation is also building community ponds in Jhor, Dharmasthali, and Chunikhel in the Kathmandu Valley to stabilized and recharge underground aquifer with support from local community. Many researches have confirmed that storing rain water in a pond can provide soil with moisture, recharge underground table as well as stabilizes slopes in the hills.

Water demand of Kathmandu ValleyA modern piped water supply system of the Kathmandu valley was introduced in 1891 in the form of the Bir Dhara Works. Until 1891, the water supply needs of the city residents were met through springs, rivers, and shallow dug wells. Stone spouts locally called dhunge dharas were common serving the three cities: Kathmandu, Bhaktapur and Lalitpur. Water from these sources was used for daily household activities. Bir Dhara supplied water to some public standposts and some to Rana palaces. To augment the increasing water needs, another system called the Tri Bhim Dhara was built in 1928, which was administrated by Pani Goswara. Today NWSC is responsible for administrating drinking water service to the districts of Nepal. The pipe networks covers a total area of about 50 km2 in Kathmandu and Patan and comprises around 100,000 taps today (Dixit, 2002). From the last two decades, the population of Kathmandu Valley is also increasing at the average growth rate of 4.04. The current population of valley is 11,68,000 and if this growth rate continues, the population of Kathmandu valley is expected to be 22,90,000 by 2020. With the uncontrolled population growth, pressure is increasing on the drinking water. On one hand, the increasing population is polluting the fresh water resources while on the other hand; rivers and streams are diverted to meet the drinking and other household needs by the government and non-government agencies. Moench et al., (2003) writes that in 1999, the demand of water in the Kathmandu valley exceeded 155 MLD while the municipal supply system only delivered around 120 MLD in the wet and 60-70 MLD in the dry season. Today in 2005, the water demand of Kathmandu Valley have reached 214.4 MLD while NWSC can deliver only 150 MLD in the wet and 100 MLD in dry season.1 To compensate for shortage, the government is investing in a major scheme the Melamchi Project2 to divert water from a stream outside the valley and deliver it to Kathmandu through a 26.5 km long water transmission tunnel. However due to many technical problems and the ongoing Maoist Insurgency, the project is not moving forward as expected and the cost of construction is rocketing every year. Hence it can be said that water supply to Kathmandu Valley through the project is yet uncertain. One study conducted by Nepal Water Conservation Foundation shows that if we do not find alternative source of water, by 2015 (even if the Melamchi comes) Kathmandu Valley will continue to have water scarcity.

TABLE 1 WATER USE IN URBAN HOUSEHOLDSUse Washing hands/person Brushing teeth/person Toilet flush (one time) Bucket bath/person Shower bath/person Tub bath/person Washing machine/person Drinking/person Amount (litres) 0.6 2.0 15.0 20.0 25.0 80.0 100.0 3.0 Source: Dixit, 2002

The table 1 shows the minimum water requirements for different household activities in an urban area. However, due to the intermit water supply and limited water availability the distribution of water is not uniform in most places. Some places receives plenty water where as others do not receive any water at all. The above table shows that most of the water in an urban area is spent in cleaning and washing, where as only three litres is needed for an individual for a day. There are many places in Kathmandu Valley where there is not that much supply of water also. On the contrary, industrial sectors consume much more water. Even though, the supply is very limited, many household in Kathmandu Valley usually a toilet flush of 1215 liters capacity, which normally uses fresh water from the municipal supply or groundwater, extracted with centrifugal pump. If the harvested rainwater can supply this much water, around 70-80 liters of fresh water can be saved per day in a house of five family members. Also cost of electricity to run pump can be saved. If the water collected is clean, it can be used for other household purposes besides flushing toilet and water supplied from municipal supply can be used for drinking purposes only. The fact is that the State has been unable to provide even the minimum drinking water to its residents in most part of Kathmandu Valley; on the other hand the lifestyle of people is changing affecting their water consumption habit. The water demand of an individual household is increasing while water supplied is decreasing. In parallel, the population is on increase and the question remains as to when the residents of Kathmandu Valley will have sufficient drinking water? If not what are the alternatives?

Alternatives to Municipal Supply Dhunge dharasStone spouts often called dhunge dharas are a popular source of water. The water collected is used for washing clothes, drinking, bathing and for other household purposes. Few conduits are also believed to have healing powers against certain diseases like arthritis, goiter catarrh (commonly called pinash). These systems are still used in most of the parts of Lalitpur and Bhaktapur. Most of these dhunge dharas were built during Lichhavi and Malla era. Water quality of dhunge dharas: Even though the supply system of such spouts were systematic, the population explosion and uncontrolled urbanization is creating stress on these structures often polluting and damaging the recharging channels causing them to dry out. Similarly, wastes piling around the spouts are blocking the drainage network and the stagnant water is becoming a breeding of vectors that transmit water borne diseases. During the monsoon, nearly all dharas show high level of fecal coliform contamina-

tion (Moench et al., 2003). In one study conducted by ENPHO (1990), all 21 samples taken from Kathmandu city was contaminated with fecal coliform. The lowest average faecal coliform densities were observed in the taps of Bhatbhateni (8 col/100 ml), Balajutar (1 col/100 ml) and sundhara (19 col/100ml) whereas the highest coliform densities were observed in Bhimsenthan (37602 col./100 ml) and Narayanhity (15, 198 col/100ml). 3 The study further concluded that overall 81% of the taps contained an average density of more than 100 col/100ml. The contamination was high during the monsoon. The surface pollution is the main cause of groundwater and stone spout pollution, In August 2000, a spout called Alko hitti was discharging blood and decaying pieces of meat from its tap which was believed to be seeped into the water network from a nearby bone factory. This incident caused many individuals to suffer from diarrhea who consumed water from the spout. However, most resident still perceive water from dhunge dharas to be good and safe to drink (Whittington et al., 2002; Cf. Whittington and Lauria, 2003). Many of such dharas are still used for cooking and drinking in Kathmandu Valley. The Alko hitti mentioned above has been highly exploited to meet the drinking water of people of ward no 22 at Lalitpur. The local authorities of ward no 22 built a tank to catch nighttime water and have been supplying to individual houses through pipes. People normally boil and filter the water received from spouts.

GroundwaterThe insufficiency of the municipal supply creates environment of water scarcity and for the development and use of an alternative water sources. The most probable ones are underground water, water vendors or develop coping strategies. In this context, the scarcity of surface water sources to provide water to homes, led the Nepal Government to the mining of groundwater resources during the sixties. In 1961, tube wells were installed at Balaju and Bode to extract groundwater. They extracted around 1.7 million and 1.96 million litres of water per day (MLD) respectively.4 By the end of 1989, the estimated groundwater abstraction from 60 tubewells was 14 million m3. Of the 60 wells 28 belong to NWSC (HMG, 1990). Besides NWSC, Private hotels, domestic households, government institutes, embassy, factories and industries have exploited the groundwater resources extensively. At present the total extraction of groundwater in the Kathmandu Valley has been estimated as 46.86 MLD.5 The extensive use of deep unpolluted aquifers under the Kathmandu Valley is suffering from overdraft. The piezometric levels in wells of NWSC have shown a lowering of 15-20 metres in the period between 1985-1995.6 According to JICA (1990) and CES (1992)7 , the abstraction (50 MLD) have exceeded the recharge (27 MLD) by about a factor by two, as a result groundwater level are dropping at about 2.5 m /year. This is not only the case of Kathmandu valley, as groundwater depletion has become a major problem all over the world. For example, during the last 30 years, in Coimbatore district, the number of wells has doubled but the net areas they irrigate have marginally increased. Along with this, the number of wells abandoned in the districts increased from around 4, 000 in 1960 to about 16, 700 in 1990 (Palanasami and Balasubramanian, 1993 Cf. Moench et al., 1999). This shows that the groundwater resources of the region are fully developed and new wells are in competition with existing ones for the limited available supplies of groundwater (Moench et al., 1999). Groundwater quality: For the past few decades the over population and city encroachment have extensively caused water pollution. Not only surface water but also groundwater has become polluted. CEDA (1990) and ENPHO (1993) identifies that the groundwater in the urban areas is severely polluted by human waste.8 Most of the studies have shown that there is high fecal coliform in the shallow ground water. However, the full impact of groundwater pollution to public health has not fully been assessed. BBWMSIP (1994) mentions that the water quality does not meet the WHO standards for drinking water

although it is an important source for many people since the municipal piped supply is inadequate to the kathmanduities. Pedley and Howared (1997)9 observed that the contribution made by groundwater to the global incidence of water borne diseases cannot be assessed easily; for many countries the incidence of waterborne disease is not accurately and the data for groundwater usage are not available, where the public health statistics are available, the data are insufficient to determine the source of the water involved in the transmission of the disease. However, deep underground water is free from organic contamination but being fossil water, they contain high amount of minerals (JICA, 1990; Cf. BBWMSIP 1994). ,

Water VendorsFor the past few years, the private water markets have emerged as an alternative sources. On one hand, the bottled waters are gaining popularity while on the other hand, private tanks have become major water vendors in the urban areas of Kathmandu and Lalitpur where municipal supply have failed. Moench, Y. (2001) mentions that both of these markets are completely unregulated, leaving the price to be determined by the competitive market and water quality discretion of the individual company. In another words, the monopoly of vendors on price and quality exists. There are hundreds of private tankers supply water to urban areas of Kathmandu and Lalitpur

Rainwater HarvestingThe above scenario shows that the only water available in Kathmandu Valley beside polluted river water, is in the form of underground, which are extracted by all sectors, viz. individuals, hotels, commercials, and government. These resources need to be recharged gradually so that it would supply water in a sustainable way. With the current trend of migration, the only probable recharging area in the northern part of Kathmandu is under heavy urbanization. The heavy engineering structures which are increasing every day are preventing the water to percolate thorough this permeable soil. Similarly, the rising population is also causing surface and groundwater pollution in most cased undrinkable. On the other hand, with the groundwater level decreasing (increasing cost of pumping); monopolizing water prices by water vendors; and the intermit supply of NWSC, there is no other option for the residents other than tapping rainwater. This method is very cost effective and guarantees relief. It is also evident from above that there are no other possible water sources around the Kathmandu Valley, which could be tapped and supplied beside Melamchi, whose faith is also uncertain. Therefore the only feasible way to fulfill water needs of the Kathmanduties is by installing rainwater-harvesting systems. Rainwater-Harvesting Systems can be built in individual houses, government offices, commercial buildings or public places.

Water Harvesting SystemsThere are different types of rainwater harvesting systems depending on the land topography, the slopes and the rock types. The systems can be of both household and community level depending on the nature of collecting systems and volume of water collected. HMG/N (1998)10 has identified following systems, which can be used to store water and use later or can be used to recharge underground aquifer. Among the listed systems, the most popular and widely practiced systems are the surface and rooftop harvesting systems. 1. 2. 3. Rooftop Harvesting Surface Harvesting Rock Catchment

Box My Rainwater Harvesting SystemThe area where I live (Tahagalli, Dharahara) has been always a water scarce area although in the heart of the Kathmandu Valley. With the increase in use of centrifugal pump and unplanned urbanization, the area is heavily under water stress. It has been years since we receive water at our taps. Those who could pump water often complain about receiving contaminated water from their taps, often-raw sewage. Today we heavily depend on water vendors to meet household needs. It has been over six years that I have been buying drinking water from vendors. To combat the water scarcity, I built rainwater-collecting system. Now I collect rainwater from my terrace, which has a catchment area of about 670 square feet. For storing rainwater, I have also built underground Reinforced Cement Tank of 4000 liters capacity. To filter our large and heavy materials (mostly, sand particles), I have used a settling tank of 4.5 cubic feet [1.5' x 1.5' x 2.0'] before sending rainwater directly to the storage tank. The collected rainwater has been used for all other household activity except drinking. That saves me lots of fresh water, which I buy from water vendors. Normally, in the monsoon it takes two-three days to fill my storage tank depending on the rain intensity. While during the non-monsoon period, I use groundwater for the household activities. To compensate the used groundwater, I have built 7-8 feet deep soak-pit, which receives, overflowed from RC tank and infiltrates it into the ground.

Collection pipe

Underground collection tank

Settling tank

4. 5. 6. 7.

Excavated Reservoirs Earthen dams Underground and sub-surface dams and Sand dams

Surface-harvesting system: It catches rapid run-off from natural or man-made surfaces, then concentrates and stores it. This stores water which otherwise would have gone to river as a run-off, evaporated back or percolated. Water collected by this method is comparatively non-drinkable, however, it can be used for purposes other than drinking like, cleaning, washing, watering cattle, and irrigation. In Kathmandu Valley there were numerous ponds, which collected rainwater from agricultural runoffs however, with the human encroachment such ponds are being replaced with engineering structures. However, there are examples where such water is treated and used for drinking. Singapore collects rainwater from the airport and is supplied to the main system of drinking water after treatment. Rooftop-harvesting system: Rooftop harvesting system is highly practiced in most of urban and suburban areas where there shortage of municipal supply. The idea is to catch the rain falling on the roof and store it for later use. This is gaining popularity in a water scare areas all over the world specially. In Nepal this system has been installed in both urban and rural areas. Usually, house roof made of cement and corrugated Galvanized Iron (CGI) sheet is used for the collection of rainwater. Tile, slate and thatch roofs are also used. The quality of water collected depends on the surface where it is collected. Water from cement roof and CGI is comparatively clean than collected from other types. However, the surface of the roof must be cleaned and maintained regularly as there would be lots of dust particles and food and debris brought by birds. First rainwater of monsoon should not be allowed to flow in the collection chamber or tank. A simple mechanism called foul flushed can be installed as point out by Ajay Dixit in his book Basic Water Science. The foul flush is placed in the inlet pipe in front of the tank. In a normal RHS system, a gutter, pipe, tap and a tank is needed. People use different kinds of storage tanks to store rainwater. Some of which are polythene, Ferro cement or local bitumen drum. The tank is often covered to prohibit entry of pollutants. Rainwater from the roofs is diverted by means of gutter and pipes to bring into a tank. However, the design and the materials used differ with the houses. The amount of water collected depends on the roofing area, size of tank and the amount of rainfall. Generally average people prefer tank of capacity 100-500 liters to store water. However some household even uses a bigger capacity tank as much as 2000-4000 liters. In the community system there may be of different capacities to meet the need of many households. The amount of water collected depends on the amount or rainfall or precipitation and the roof area. Dixit (2002) have provided a graph (Table 2), which can be used to estimate the volume of water that will be collected from a particular area.

Potentiality for Groundwater Recharge in Kathmandu ValleyKathmandu valley with the shape of circular basin has an area of 656 km2. The central part of the valley consists of flat lands at elevation of 1300 m and high mountains on all sides surround the flat land. The main river the Bagmati runs from the center of the valley from north to south.

TABLE 2 RAINFALL AREA AND VOLUME OF WATER COLLECTED (M3)Area (m 2) 40 80 120 160 200 250 300 400 16 32 48 64 80 100 120 600 24 48 72 96 120 150 180 800 32 64 96 128 160 200 240 Effective rainfall (mm) 1,000 40 80 120 160 200 250 300 1,200 48 96 144 192 240 300 360 1,400 56 112 168 224 280 350 420 1,600 64 128 192 256 320 400 480 1,800 72 144 226 288 360 450 540 2,000 80 160 240 320 400 500 600 Source: Dixit, 2002

Kathmandu valley is composed of two series of geological successions: Quaternary (overlies lower portion of valley) and Precambrian to Devonian (surrounds the valley) (HMG, 1990). The ground surface of the valley bottom is flat. The buried bedrock is estimated to be irregular in shape. The thick geological deposits of the flat part consist of lacustrine deposits and fluvial deposits (Ibid). The northern mountainous part of the valley consists of arenaceous deposits, which are composed of coarse to medium grained sand with rock fragments. This is the part where most of the underground recharge takes place. Most of the Nepal Water Supply Corporation (NWSC) wells are located in this part of the valley because the area has best aquifer condition for the groundwater development compared with other parts of the valley. Argillaceous deposits composed of the clay materials underline the southern mountainous areas. Intermediate types are found in the central part of the valley from west to east, between the areas composed of the arenaceous and argillaceous deposits. Materials of these types are composed of clay or clayey silt with intercalations of sandy layers and clayey layers, which are mostly impermeable. High potentiality for groundwater recharge is expected only in the northern part of the valley. This permeable layer is usually brought by erosion of limestone and phyllites. Dipak Gyawali points out in his book Water in Nepal that within the catchment area of 656 km2, the average rainfall that Kathmandu Valley receives is 1500 mm every year. He further assumes that if half of the available rain either evaporates or percolates into the ground, about 500 million m3 of rain will still be available for capturing. If an individual requires 100 liters per capita per day (LCD), which is double of the standard assumed for rural area, and if only six percent of the 500 million m3 were harvested, Kathmandu could meet much of its water needs by allocating less than 1.5 % of its area for tanks, and other water harvesting structures with an average depth of only two meters. With this assumption it can be said that if the individual households could collect rainwater it will be enough to meet their domestic needs. The collected water can be used for other purposes besides drinking like: washing clothes, bathing, using in toilet flush, washing utensils etc, whereas the treated fresh water received from NWSC can be used for drinking.

At the EndWith the increasing demand of water both in industries and household, and on not receiving the supply, the residents in most of the places have started to install rooftop-harvesting systems in their individual houses. Which is a very efficient water management technique. Capturing and tapping rain has to be mandatory in all urban houses as in the case of Gujarat where Urban Development Departments has made

roof water harvesting mandatory for new building complexes of 1500 m2 and above. Beside, if we could harvest rain in the airport and other government-owned and public buildings, much of water problem would be solved. Collecting rainwater is not the only option to solve problem, water also should be use efficiently. All the 3Rs i.e. Reduce, Reuse and Recycle should be applied for proper water management. If this can be done, almost 90 percent water problem of Kathmandu valley would be solved.

BibliographyAgrawal, A. and Narain, S. (eds.), 1997: Dying Wisdom: Rise, Fall and Potential of Indias Traditional Water Harvesting Systems, Centre for Science and Environment, New Delhi. Dixit, A.2002: Basic Water Science, Nepal Water Conservation Foundation, Kathmandu. Gyawali, D., 2001: Water in Nepal, Nepal Water Conservation Foundation and Himal Books, Kathmandu. HMG, 2004: Arsenic Testing and Finalization of Groundwater Legislation, Proceeding of the seminar on Arsenic Study in Groundwater of Tarai and summary project Report, Department of Irrigation, Kathmandu HMG/N, 2001: Position Paper, Achieving Environmental and Community Through Integrated Water Resource Management and Strengthening of Municipal Government in Nepal, Water Optimization Pilot Project, Ministry of Physical Planning and Works, Kathmandu, Nepal. HMG/N, 1998: Final Report for Study of Rain Water Harvesting in Tansen, Palpa, His Majestys Government, Water and Energy Commission Secretariat, Kathmandu. HMG/N, 1990: Groundwater Management Project in the Kathmandu Valley, Final Report, Nepal Water Supply Corporation, Kathmandu. Mathema, P 2005: Empty Water Pots Even in Water Day (in Nepali: Pani Dibas Ma Pani Nabhariyaka ., Gagriharu ), Gorkhapatra, March 25. Moench, M., Dixit, A., Janakarajan, S., Rathore, M. S. and Mudrakartha, S., 2003: The Fluid Mosaic: Water Governance in the Context of Variability, Unvertainty and Change, A Synthesis Paper, Nepal Water Conservation Foundation and Institute for Social and Environmental Transition-International, Kathmandu and Boulder. Palanswami, K., Maylswami, C, Raviraj, A., and Dhanalakshmi, G., 2003: Rainwater Harvesting, Water Technology Centre, Tamil Nadu Agricultural University, Coimbatore. Sainju, M. M., Malla, S. K., and Thanju, J. P 2000: Policy and Institutions for Water Harvesting in Nepal, ., Mahesh Baskota and Surej R. Chalise (eds.) Waters of Life: Perspectives of Water Harvesting in the HKH, International Center for Integrated Mountain Development, Kathmandu Whittington, D. and Lauria, D. T., 2003: An Economic Reappraisal of the Melamchi Water Supply Project (Nepal), A Report to the Asian Development Bank, Prepared in collaboration with Acres International, California.

Notes1 See Mathema, 2005 2 HMG/N is implementing the project with support from Asian Development Bank, NORAD, SIDA, OPEC Fund, the Nordic Development Fund and the Japan Bank of international cooperation. 3 Today many of these taps have dried out. Sundhara, which stop functioning was believed to be separated from its network during the construction of Karmachari Sanchaya Kosh building. 4 See Gorkhapatra 1961, June 6 5 HMG, 2001. 6 HMG, 2004: Arsenic Testing and Fianlization of Groundwater Legislation, Proceeding of the seminar on Arsenic Study in Groundwater of Tarai and summary project Report, DoI., Kathmandu. 7 Cf. BBWMSIP 1994 , 8 Cf. BBWMSIP 1994 , 9 Cf. Bruke and Moench (2000) 10 HMG/N, 1998: Final Report for Study of Rain Water Harvesting in Tansen, Palpa, His Majestys Government, Water and Energy Commission Secretariat, Kathmandu.