Theme 6-16-Impact assessment of conservation measures in arid areas - A case study of Osian-Bigmi (Jodhpur) watershed.

Abstract

Impact evaluation of a watershed management programme is essential to know an overall assessment of the technical results of the different soil and water conservation measures adopted in any watershed area. It also helps in knowing the appropriateness of the method employed in carrying out the project activities and also to estimate the medium and long term social and economic benefits of the activities, efficiencies and impact of the project in the context of its stated objectives.

Keeping in view the importance of the post project evaluation a study was conducted to assess the impact of various soil and water conservation measures adopted in Osian-Bigmi watershed project. The paper presents a field study of impact evaluation of soil conservation measures in one of the watersheds of Jodhpur Regions. Osian-bigmi watershed is situated between 27o 37’ N to 26o43’ N latitude and 72o51’30” E to 72o56’E longitude in Jodhpur district at about 60 Km away from Jodhpur on Jodhpur Phalodi road. Watershed covers an area of 4667 ha and is bounded by low ridges of stony wastelands and sand dunes. The watershed area is characterised by arid climate with aridity index varying from 70 to 87 and increases from south east to northwest. Rainfall in watershed area is low( 338 mm yr-1) with high degree of variability in terms of distribution and quantum. Prior to start of watershed management project area were devoid of any kind of good vegetation. The area is predominantly covered by moderately deep to deep soil, underlying with loose lime concretionary horizon. The surface soil is coarse sand and loamy sand. As per land capability classification most of the area falls under land class IV and above leading to severe limitation of reduced choice of plants for conservation purposes. Soil erosion in different forms was another problem encountered in the watershed. Watershed area was treated as per land capability classification and various engineering and agronomical measures were adopted in watershed area.

Post project evaluation of the watershed area revealed that significant improvement in crop yield with an additional income of Rs., 2378 ha-1 yr-1. The rate of silt deposition was found to reduce by 3.68 m3 ha-1 year-1. The soil fertility have also changed in terms of increase in available Phosphorous, Potash and organic carbon. The ground water recharge in the watershed area and adjacent to watershed have reported of rising trend. Thus the benefit cost ratio was found to be more than 1.0 and showed that such a project is economically viable for arid region of Jodhpur district.