60 CHAPTER-IV Rain Water Harvesting 4.1 General: Rain water is the main source of fresh water which is available annually through the hydrological cycle. The principle of water harvesting is collection and storage of the rainwater when and where it falls. Major portion of available rainwater goes unutilized in the Himalayan region mainly due to its distribution pattern and topography of the area. About 80% of annual rainfall occurs in three months during monsoon. The only option is to harvest this rainwater and to store it for lean season. In the areas where slopes are steeper, overland flow gets flushed of very swiftly resulting in non-availability of water in peak water stress period even through the average rainfall is very high. In such areas efforts should be made to harvest maximum rainwater, possible by constructing suitable water harvesting structures to artificially recharge the ground water and store water for domestic use by constructing roof water harvesting structures and water harvesting structures. Integration of Remote Sensing and Geographical Information System (GIS) techniques provides reliable, accurate and updated database to identify suitable sites for water harvesting such as farm ponds, ground water recharge zones, check dams, percolation tanks, nala bundh and shaugel pond etc. The population of the Dabka watershed is completely dependent on spring water for their daily needs. The increased population pressure and declining trends of spring discharge has caused severe water shortage in the area. For the optimum use of the available water resources in the catchment, it is necessary for conservation of the water resources in the area. The area, Dabka watershed comprises fifteen villages out of which, seven villages namely Bansi, Ghughukhan, Sigri, Saur, Dola, Baghni, Jalna have been found to face severe water scarcity during water stress periods of the year. Beside these villages some parts of other villages and grazing lands located at comparatively head ward region of the area have been found to suffer from this Estelar
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CHAPTER-I V
Rain Water Harvesting
4.1 General: Rain water is the main source of fresh water which is available
annually through the hydrological cycle. The principle of water harvesting is
collection and storage of the rainwater when and where it falls. Major portion
of available rainwater goes unutilized in the Himalayan region mainly due to its
distribution pattern and topography of the area. About 80% of annual rainfall
occurs in three months during monsoon. The only option is to harvest this
rainwater and to store it for lean season. In the areas where slopes are steeper,
overland flow gets flushed of very swiftly resulting in non-availability of water
in peak water stress period even through the average rainfall is very high. In
such areas efforts should be made to harvest maximum rainwater, possible by
constructing suitable water harvesting structures to artificially recharge the
ground water and store water for domestic use by constructing roof water
harvesting structures and water harvesting structures. Integration of Remote
Sensing and Geographical Information System (GIS) techniques provides
reliable, accurate and updated database to identify suitable sites for water
harvesting such as farm ponds, ground water recharge zones, check dams,
percolation tanks, nala bundh and shaugel pond etc. The population of the
Dabka watershed is completely dependent on spring water for their daily needs.
The increased population pressure and declining trends of spring discharge has
caused severe water shortage in the area. For the optimum use of the available
water resources in the catchment, it is necessary for conservation of the water
resources in the area.
The area, Dabka watershed comprises fifteen villages out of which, seven
villages namely Bansi, Ghughukhan, Sigri, Saur, Dola, Baghni, Jalna have been
found to face severe water scarcity during water stress periods of the year.
Beside these villages some parts of other villages and grazing lands located at
comparatively head ward region of the area have been found to suffer from this
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issue. Therefore, to make the availability of water throughout the year for
domestic, animal husbandry and local agricultural use, an attempt has been
made to conserve water thorough rainwater harvesting methods. In this regard
an attempt has been made by conducting pilot studies in few selective villages,
to assess the conservation of water.
Irrigation is very essential for the survival of agricultural crops in rainfed areas
where slopes are steep and dry. The excess rainwater has to be conserved or
stored in different storage structures, which can be used later. Water harvesting
systems have largely focused on the technology of roof top in catchment areas.
Usually the roof is made of tiles (roof stones), iron or asbestos sheets. It is
connected by gutters and down pipes to one or more storage containers ranging
from simple ponds to large cement tanks.
4.2 Methodology for Rainwater Harvesting:-Site selection for water
harvesting structure, the technical guidelines of Integrated Mission for
Sustainable Development (IMSD), prepared by National Remote Sensing
Centre (NRSC), Indian National Committee of Hydrology (INCOH) are used
in the present study. On the basis of structure, lithological, geomorphological,
socio-economical conditions, check dams and shaugel pond are proposed in the
study area.
For the site selection of Check dams lower order streams up to third order (Fig.
4.2) with medium slopes are taken. Check dams are proposed where water table
fluctuations are very high. The slope of the region was considered flat to
gentle, so that the maximum quantity of water could be stored.
Farm ponds can be proposed within individual farms. The main aim for the
construction of Farm ponds is, i) to provide water storage for life saving
irrigation in a limited area, ii) to provide drinking water for livestock and
human beings in arid areas, iii) to serve as water storage for providing critical
irrigation to a limited number of fruit plants for establishment purpose.
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Nala bundhs and percolation tanks are structures constructed across nallah or
streams for checking velocity of runoff, increasing water percolation etc. Nala
bundhs are less expensive which is smaller in dimension and constructed
usually by local material. The percolation tanks are large and more expensive.
The main aim for construction of Nala bundhs and Percolation tanks are i) to
impound surface runoff coming from the catchment and to facilitate percolation
of stored water into the strata to raise the groundwater level and ii) to hold the
site flow.
4.3 Site selection for harvesting:-The area under investigation comprises of
very rugged topography which includes hillocks with steep slopes, escarpments
with cliffs and long narrow ridges. Apart from the area comprises of tightly
folded and faulted rock terrain with closely spaced fractures and shears. The
available formation exhibits their respective attitudes vary in different
directions. Hence, the configuration of formations in the area is found to be
dominantly manifested with the fracture porosity and bedding planes in
different directions. However, the intensity of the distortion of such directions
is found increasing towards the main thrusts. So, construction of recharge wells
may not feed recharge to the right desired directions. The area receives an
annual average rainfall of the order of 172.8 cm (Table 3.2). The monsoons are
found to contribute the major portions of the rainfall. The socio economical
condition of the inhabitants is observed to be based on the subsistence
agro-economy of the area, animal husbandry etc. Thus, the inhabitants are
forced to lead a difficult life. Therefore, keeping in consideration the geology,
topography and social economic conditions of the inhabitants an attempt has
been made to propose the construction of selective water harvesting structures
in the Dabka watershed so that their living condition could be improved
(Fig. 4.2).
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Three types of structures may be recommended for the area
(i) Shaugel ponds
(ii) Check dams
(iii) Farm ponds
(i) Shaugel Ponds: - Shaugel ponds for rainwater harvesting and overland
flow interception have been proposed in the area. The different feasible locations