Watershed Prioritization For Soil Conservation Planning With
Mos-1 Messr Data, Gis Applications And Socio- Economic
Information
A Case Study Of Tinau Watershed, Nepal
Shyam Sundar Shrestha, Kiyoshi Honda And Shunji Murai
Space Technology Application And Research Program
Asian Institute Of Technology
Abstract
Nepal is a mountainous country with many watershed and sub watershed covering the catchments of many rivers and lakes throughout the country. However, the rapidly increasing population and the consequent loss of forest and the intense agricultural land use in the slopes has resulted in degrading watershed in most of the districts. Since it is not possible to launch watershed management projects all over Nepal at the same time, it is very important to use some method to prioritize watershed on the basis of soil degradation status of various watershed. This study is an attempt in this direction by using remotely sensed data, together with socio economic data and other data on a GIS environment to assess the watershed conditions for a watershed in western Nepal.
Introduction and the Study Area
The study area is called Tinau watershed, and is located in the district of Plapa in western Nepal. The watershed has a total area of 333 square kms and consists of seven subwatersheds. The geographical coordinate of the study area from 27045'00" to 270 52'52" and 83025'30" to 43042'30" E. Most of the watershed falls in the lower Mahabharat range of mountains and the elevation from 330 meters to a maximum of 1893 meters. The average annual precipitation recorded at one of the stations in the watershed is 1494 mm.
Materials and Methods
The following data have been used for this study:
-
Satellite data, MOS-1b, Path /row 056/081, acquired on January 26,1993 and Landsat TM path/row 142/41, quadrant 3,4, acquired on November 26,1990.
- Aerial Photographs acquired on November and December 1990, approximate scale 1:50,000.
- Topographical maps 1:25000 and 1:50000 from Department of Survey, land use, land system and land capability maps at 1:50,000 developed by Land Resources Mapping Project (LRMP) based on aerial photographs of 1978.
- Geological maps district administrative maps etc.
- Data from socio economic survey at the field and the population, climatic and other data available from various offices.
In the evaluation of areas for watershed prioritization, a term called soil Erosion status (SES) has been defined as follows:
| SES = |
LEA*10+MEA*20+ HEA*30
-------------------------------------------
Total Area |
Where,
SES= status of the subwatershed,
LEA= low erosion area
MEA medium erosion area, and
HEA= high erosion area
