Identification of Suitable Sites for Water Harvesting Structures in upper Betwa Watershed through Waris



Analysis through Waris for identification of Structures

Selection of theme: WARIS provides an option to user for selection of themes to be used in the identification of structures. The major themes selected for the analysis are shown in figure 1. The themes are land use / land cover, soil, slope and hydro geomorphology. The selected themes are combined together in GIS environment.


Figure 1

Extraction of buffer area: The water harvesting structures are preferred along streams and 500 m area on either side of the river is sufficient. Buffer of 1 km is extracted for 2nd and 3rd order drainage only. Drainage of lower order is not selected, as these drains will not be able to give required volume of water. Velocity and volume of water in higher order drainage are also avoided by not selecting them.

Defining weights: WARIS provides interactive facility to provide weights for all categories in each theme. Different weights can be given for water harvesting and recharge sites. Weights are given according to structure for which analysis is being carried out. E.g. for nala bund less than 2 percent slope is preferable, where as for anicut 2 to 8 percent slope is required.

Selection of suitable zones: Cumulative weights are then calculated for each polygon in combined output. Total weights are divided in three zones for further analysis. The three zones are most suitable, more suitable and suitable. Figure 2 shows the suitable zones for structures. Statistics of suitable zone map was calculated. An area of about 57 sq km was found to be in most suitable zone for identification of water harvesting sites. More suitable zone occupies 453 sq km of the watershed and suitable area covers 523 sq km area.


Figure 2

Identification of water harvesting sites: The suitable zone map thus prepared was used for identification of water harvesting sites. Following structures were suggested as shown in figure 3.


Figure 3

  • Anicut: For anicut sites buffer of 1 km was constructed around 2nd to 3rd order streams. Medium slope areas between 2 to 8% were taken. Favorable soils were given weights to allow storage of water. A total of 10 sites were marked in the area.
  • Nala bund: Nearly plain, (up to 2%), upper reach, catchments greater than 40 ha, permeable soils were the criteria according to which the weights were decided. After the analysis 16 sites were marked which are suitable for nala bund.
  • Farm pond: Flat topography, low permeability, absence of faults, joints were the criteria for site suitability.
  • Dug cum bore well: Lineament map pertaining to study area was studied and 9 suitable sites were marked on the output.
Conclusion
Generation of water resource development plan is a tedious task but a guided semi automated way helps analyst to achieve the task in a better and faster way. WARIS helps in identification of suitable sites. Its facility to take user input for providing weights to the entire category makes it versatile to be used in all types of terrain. For Upper Betwa watershed area, around 4.17 % area, which falls in most suitable zone, is further chosen for identification of water harvesting sites. Total 38 sites for different structure were suggested within study area.

Acknowledgement
The authors wish to acknowledge the help and support received from Shri S Adiga, Director NNRMS/RRSSC during course of study.


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