GIS OPTIMIZATION OF RAINWATER HARVESTING IN GHAZI TEHSIL, DISTRICT HARIPUR

Abstract

Rainwater harvesting is an important practice in order to improve the water availability and agricultural productivity in the arid and semiarid areas. This is particularly useful in areas with reasonably high annual rainfall where the shortage is caused primarily due to excess surface runoff and secondarily due to the absence of water conservation practices. It presents a great challenge to identify the potential optimal sites for rainwater harvesting on a large scale. In this study an attempt has been made to use geoinformation technologies to identify areas optimally suited for rainwater harvesting in Ghazi Tehsil of Haripur district of Khyber Pakhtoonkhwa province, northern Pakistan. Additionally, site-specific application and adaptation of rainwater harvesting techniques was also evaluated. Using HECgeoHMS tool of ArcGIS 9.3, the curve number was used as input parameter in the US Soil Conservation Service (SCS) runoff estimation method to compute the surface runoff potential for different combinations of landcover and hydrological soil groups (HSG) in the study area. Various thematic maps of the area, such as surface slope, drainage network, rainfall, landcover, landuse, soil, geology and proximity analysis maps were generated in GIS to perform weighted overlay analysis. Reclassification of above mentioned layers were performed and weights were assigned according to technical guidelines suggested in the literature namely Integrated Mission for Sustainable Development (IMSD), Indian National Committee For Hydrology (INCOH), Food and Agricultural Organization (FAQ), also keeping in view the study area topographic and climatic conditions, in order to identify the potential sites for rainwater harvesting. About 28.73 percent of the area is suitable, 51.72 percent is less-suitable and 19.55 percent is not-suitable. Relative suitability was assigned to the results of suitable sites for rainwater harvesting. This was further used as input in order to identify the potential sites for different rainwater harvesting structures like 1Farmponds', 'Check-dams', 'Nigarims' and 'Gully-plugs'. The study results revealed that 10.63 percent of the area was suitable for Farm-ponds, 5.75 percent area for Checkdams, and 13.79 percent for Nigarims and percent of the area suitable for Gully-plugs. The small dams organization at Peshawar had conducted field survey and suggested two sites namely Site A (Khairbara) and Site B (Kotehra) in the study area. In order to compare the GIS derived and field based results, it was evident that field based derived results were exactly overlaid on GIS results of Check-dams, Gully-plugs and Nigarims.