Gravity based spring water supply systems in Andhra Pradesh: Lessons and steps towards the future

Guest post by –

Rahul Bakare

 This article details an example where local knowledge has been used to develop access to safe water in the tribal areas of the Eastern Ghats in Andhra Pradesh

The Eastern Ghats are a discontinuous range of mountains along India's eastern coast. The Eastern Ghats run from West Bengal state in the north, through Orissa and Andhra Pradesh to Tamil Nadu in the south. They are eroded and cut through by the four major rivers of southern India- Godavari,  Mahanadi, Krishna, and Kaveri.

Geologically the Eastern Ghats comprises of typical assemblage of Charnockite and Khondalite groups, Migmatitic Gneisses, Granitoids and Pegmatite, all metamorphosed in high-grade Granulite facieses. This area has rich deposits of Bauxite and Manganese ores.

Fig 2: Metamorphic Charnockite rocks in the area

Geo-politically this area was neglected till the exploitation of this pristine area with its primitive tribal population started in 1980’s. As the economic liberalization in the early 90’s required India to explore and use the homegrown natural resources to satisfy its 8-10% GDP growth, the underdeveloped Eastern Ghats  were the first to go on the block. With the Central and State Governments rolling out red carpets to many, the entry of mining companies was imminent. The tribal populations who were mostly forest gatherers saw the roads getting broader overnight while they did not even had a bullock cart. The undisturbed forests and the water resources were exposed to heavy pollution by mining activities. Many dams were constructed and in a few cases entire rivers were diverted to quench the thirst of the mammoth steel plants in the neighboring state of Orissa. This resulted  in widening the existing gap between rich (urban)and poor (rural) populations. Without any proper rehabilitation, this development also caused mass displacement of the tribal folks into neighboring states. When the livelihoods and lives of the poor landless tribals were threatened and the Corporate-Government nexus did not pay any heed to their peaceful demonstrations, the modern day Robin Hoods (Naxals) were born. The rampant spread of Naxalism was the ultimate product of the Urban-Government-Corporate axis. These core issues still plague this region and development has distanced itself from the region due to government apathy and the anti-establishment popular extremist movement.
 

Local Communities

The Government of India has identified 75 primitive tribal groups  located in 14 states and Union territories. At present, there are 12 such groups in Andhra Pradesh. They are Bodo Gadaba , Bodo Poroja , Chenchu , Dongaria Khond , Gutob Gadaba , Khond Poroja , Kolam, Konda Reddy, Konda Savara , Kutia Khond , Parengi Poroja and Thoti.

Konda Savara

According to the 1991 census, the total population of Khonds in Andhra Pradesh is 66,629. TheKhonds are concentrated in the densely wooded hill slopes of the Scheduled areas of Visakhapatnam district of Andhra Pradesh. They are the settlers from the state of Orissa who have been displaced due to the construction of Balimela dam. Most of these landless settlers are agricultural laborers and have a heavy dependency on forest produce or practice Jhum cultivation. Traditionally, Konda Savaras are shifting or swidden cultivators.

Savaras of Seethampeta mandal, Srikakulam district, have indigenous engineering skills in diverting the perennial water sources from top of the hills for cultivation. In terrace cultivation, they level the field just like steps of a staircase and allow the water to flow from the plot on a higher level to the plot at a lower level. They use flaps of banana trunk as water pipes to facilitate free flow of water from one field to another field. They also feel guilty about cutting trees.

 

 Figure 3 Women of the Kondu Savara tribe 

The tribal population is below poverty line due to various reasons. Lack of basic infrastructure such as water, sanitation, electricity and transportation has caused immense damage to the livelihood of these people. Population increase has led to a decrease in the per-capita land holding. Mostly rainfed agricultural crops such as rice, beans, and groundnuts are enough for subsistence but not for generation of any disposable income. Lack of transport facilities has been exploited by the local middlemen who buy the farm produce from the locals at one tenth of the retail price. A case in point, farmers from A.Sanivaramu village walk for more than 10 kilometers and sell a 20 kg bag of Guava for Rs 40 to a local trader in Santa (local weekly bazar). The same guava is sold in cities like Vizag, Bangalore, Hyderabad for Rs 20-30 Rs/kilo. Lack of financial literacy means that any disposable income is not saved, but spent in festivals or consumption of liquor. The state of education in these villages is appalling. Under a single roof classes for first till seventh standard are conducted. In many cases there are less than two teachers undertaking these classes apart from cooking the daily midday meal for the students. School toilets that are constructed under the Sarva Shiksha Abhiyan (SSA) are in utter dysfunctional state as no running water is provided. The eerie looking sanitation blocks are far from the TSC guidelines and are sheer wastage of resources.

The challenge

As the hard rock shallow aquifer systems are unexploited in this heavily forested region, there are perennial base flows in the streams and springs. However, these sources are either far from habitations or are having water quality issues due to anthropogenic pollution such as open defecation, improper use of water, lack of source protection, etc. The drudgery surrounding water and sanitation in this undulating terrain could have been solved easily by use of gravity based water supply systems but this traditional and non-engineering solution is unacceptable to the establishment. The typical government implementations of borewells and handpumps for water supply system have not been successful due to improper site selection, quality of construction/equipment, lack of electricity, etc. Hence, a prominent civil society organization, VJNNS based out of Narsipattanam in Vishakhapatttanam district approached Arghyam to implement such 4 alternative systems covering 6 villages (Chitral goppu,  Diguvu pakala, Raju pakala, Rintada, A. Sanivaramu, Palada) having 470 households with a total population  of 2180 people

The solution

VJNNS over past few years has developed unique gravity based, perennial, energy-less, 24/7/365 water systems  which also filter the spring water through slow sand filter. As the whole area is beyond any TSC coverage, no toilets exist in these villages and the whole population exercises open defecation. The lack of any health and hygiene awareness compound the problems caused by water borne diseases and cause damage to the earning capacities of the families. Hence an awareness campaign and introductory sanitation block construction within schools and Anganwadis were planned to generate demand for individual toilet construction. Most of the beneficiaries covered under this program are from the scheduled tribes of Bhagata, Konda Dora, Valmiki  & Konda.

Figure 4 Defunct Government dug borewells and handpump on the backdrop of Gravity based water system implemented by VJNNS

The implementation strategies of the gravity based water system are:

• Villagers are involved from the very start of the project including identification of water source, design and laying of the pipeline.  
• Villagers contribute in the form of “Sharm Daan”, which helps them understand the underlying principle of the whole concept and builds their capacity to repair the system themselves. 
• Though the Gravity based water supply system is a low cost implementation and low on maintenance, funds required for its maintenance are raised by formation of a corpus Village Development Fund (VDF). Each household contributes Rs 10 per month for the upkeep of the system. A water and sanitation committee is formed from among the beneficiaries for maintenance of the system. As the PRIs are less effective due to the ongoing tussle between the district administration and the extremists, the VDF committees are not institutionally within the Gram Panchayat. In many cases the Sarpanch is an integral part of the VDF committee.
• Village youth are participants of the source identification, design and implementation of the system. Training on maintenance of the system and handholding support for a year is in process.
• Villagers are also be educated about the government schemes and allocated funds which they are entitled to such as MGNREGA, TSC, etc.
• Introducing water system is the first step to get involved with the villagers and to gain their confidence. 
• Identified members will be imparted special training on the aspects of technical maintenance such as replacement of filter media, chlorination of water, and maintenance of delivery systems.

Implementation of gravity based water supply system with technical details

• A discussion with the village elders is arranged during peak summer to identify the perennial sources of spring water. This provides empirical fact based temporal data.
• The catchment of these springs is traversed with the villagers noting various sources and contours
• For each source a small enclosure is created using stones, sand and mud
• The small contained structure fills with the spring water. Time to fill the structure is noted and an approximate capacity in litres estimated.
• Then the structure is breached partially for water to flow out. The velocity of water flowing out is observed using twigs of grass and time taken for the source to regain the full head.
• These observations are undertaken during two subsequent summers to come to final conclusion about the yield of the spring
• From observing many such springs a perennial spring with low transmissivity and high storativity is chosen for the water supply scheme
• Even though during summers if the spring water flow is as small as 0.1 Lit/sec it would yield about 3000 liters of water per day which is sufficient to provide water to more than 300 people at about 100 LPCD

2.    Construction of the Spring water collection box

• To protect the spring water from any anthropogenic, animal access, and other surface water contamination a spring water collection box is constructed
• The height of the box depends upon the yield of the spring
• The outlet to the collection box is provided from the side
• The outlet pipe is covered with wire mesh to filter out any undissolved solids. This mesh also acts as a flow regulator
• The outlet pipe should be as low as possible to tap water during the summers
• If there is any stream flowing nearby then preferably that stream should be diverted to avoid any entry of surface water in the collection box
• The surrounding of the collection box should be fortified and covered with boulders, stones and mud to avoid any structural damage and seepage
• Proper covering of the collection box is critical to avoid any contamination
• Cleaning of rudimentary wire mesh filter every few days is important to avoid any blocking of the outlet
• An outlet for overflow of water is provided to the collection box

Figure 5  Cross section of spring water collection box

3.     Construction of the filter tank

• A proper site should be chosen to construct the filter tank as there should be minimum of 3 meters of water column head to generate desired pressure in the distribution system and at the community tap stands
• Proper foundation is laid for structural stability of the tank
• The capacity of the whole tank structure is calculated based on the input water, filtration rate and usage estimations
• Reinforced cement concrete tanks are used to filter and store the water

Figure 7 Cross section of the filter tank

The Filter Tank has three chambers: 

• Reverse flow rapid filter: It is used to remove the undissolved solids under pressure. The inlet pipe to this filter is at the bottom of the chamber. There is a steel plate on which the big boulders, small boulders and sand are stacked in bottoms up manner .This arrangement makes sure all the higher pressure and velocity of the inlet water is reduced and minimized while passing through the filter media. A gap of few inches is provided for water to settle and cascade in the second filter tank.
• Slow Sand Filter: Unlike other filtration methods, slow sand filters use biological processes to clean the water, are non-pressurized, and need no energy supply. It has the same material and the order as that of the reverse flow filter. The water from the first tank should come slowly as with time,  a gelatinous layer (or biofilm) called the hypogeal layer or Schmutzdecke is formed in the top few millimetres of the fine sand layer. As water passes through this layer, particles of foreign matter are trapped in the mucilaginous matrix and dissolved organic material is adsorbed and metabolised by the bacteria, fungi and protozoa. The water produced from a well-managed slow sand filter can be of exceptionally good quality with 90-99% bacterial reduction. Slow sand filters slowly lose their performance as the Schmutzdecke grows and thereby reduces the rate of flow through the filter. Eventually it is necessary to refurbish the filter. This can be done by scraping off the top few millimetres of fine sand to expose a new layer of fine sand. (source: Wikipedia)
• Storage Tank: Water from the slow sand filter inters the storage tank through an opening given at the bottom
• All three chambers have an outlet at the bottom for draining while cleaning
• The filters should be cleaned every six months and the filter material should be washed, dried and treated with bleaching power.
• After the filters are regenerated water should be allowed to flow for a few hours to wash out the bleaching agent  
• The filter tank is open from top and is covered with precast cement slabs

4.    Pipeline design for connecting collection box to filter tank

• Initial survey should be done to understand the undulating terrain and if any transmission issues may arise
• The initial gradient of the outlet is crucial to generate enough velocity to avoid any air locks in the pipeline and hence an angle of 45 degrees is given till considerable extent to increase the velocity of water. This is increased water velocity helps in

i.    Creation of suction effect
ii.    Flushing out any undissolved impurities
iii.    Avoiding any airlocks
iv.    Generate pressure to generate head to overcome any humps in the pipeline

• Pipe chosen to carry water from the collection box to the filter is made up of HDPE and has a life of 10-15 years. The diameter of the pipe is chosen based on the flow requirement. Generally 2.5 to 3 inch diameter HDPE pipe is sufficient.
• No Air vents are provided to vent any locked air from the pipes
• An overflow pipe is provided for the extra water to flow before the reverse filter system and also acts as a pressure regulator

5.    Distribution system implementation

• A distribution system of small diameter HDPE pipes (1 – 1.5 inch), laid in trenches, feeds tap stands around the village.  
• Proper locations of the public stand posts are identified based on the beneficiary demand and also to satisfy a criteria of one tap stand per 7-10 families
• Tap stands have several components: a concrete post supporting a mild steel riser pipe from the pipeline up to a tap which should discharge at least 0.1 litres per second; a concrete base on which to place a bucket; a concrete apron to collect spillage; and a gutter
• With incessant water supply and leakage, good drainage is very important to prevent the breeding of mosquitoes and the development of a filthy mess. The drainage of waste water should be diverted to a soak pit or kitchen garden where it can productively used for any nutritional security of the households
• Due to higher water pressure the tap washers malfunction often and have to be replaced periodically. Alternatively, the push-cock type of taps may be tried.

6.    Raising of water to higher elevation

• In a few cases the water from the storage tank can also be lifted to a considerable head using the basic principles of siphon and hydraulics.

Approximate cost of the gravity based water supply systems 

Threats to the systems

Conclusion