Estimation of Soil Erosion using USLE and Landsat TM in Pakistan
Shigeo Ogawa, Genya Saito, Nobuyuki Mino,
Satoshi Uchida*, Nasir M. Khan**, and Muhammad Shafiq**
National Institute of Agro-environment Sciences
3-1-3, Kannondai, Tsukuba, Ibaraki 305, Japan
Tel : (81)-298-38-8225 Fax : (81)-298-38-8199
E-mail : sogawa@niaes.affrc.go.jp
*Japan International Research Center for Agricultural Sciences
**National Agricultural Research Center
Abstract
The target area (Pothwar tract) is located in the northern part of Pakistan. The agriclture in the area is predominantly dependent upon rainfall. About 60% of the mean annual rainfall occurs during the summer season as high intensity storms. Soil erosion occurs during the season by storms. But it is not easy to estimate the quantity of soil erosion in the wide area.
Universal Soil Loss Equation (USLE) has also been employed as a basis to observe the intensity of erosion using Landsat TM, rainfall data, topographic map land capacity map. The results in this case could be improved by using more accurate data and through field ground survey. Heavily eroded is occurred at bare soil and steep condition. Low eroded area is mainly field. Erosion is occurred in summer season. This method is useful for detection of land use change and environmental change.
Introduction
The land degradation is not mainly due to soil erosion, water logging and salinity but primarily due to inappropriate use of the two main natural resources (land and water). Resource use planning and management is a complex and a comprehensive exercise, based on complete and regular monitoring information system for area. Thus it is important understand the existing state of resources, their extent of degradation and potential for phase-wise improvement of environmentally sensitive areas. Traditional sources of investigation are expensive and time consuming. At the same time, federal agencies continue to incur cutback of budget, manpower and other resources while continuing to be responsible using USLE. Several studies have indicated that remote sensing data and Geographic Information Systems (GIS) can be used as a first stage input to identify and map the degraded lands (Stephen et al., 1981; FAO 1978; Evangelista et al., 1992; Rondal and Yoshida., 1992 and Uchida et al., 1994).
Study Area
The area selected for this study in the small part of this plateau near the North-east of Fatehjang between latitude 33 30' to 33 45' and longitude 72 30' to 72 45' covering an area of about 27,500m X 23, 000 m (figure 1). The elevation ranges from 300m to 500m. The mean annual rainfall varies from less than 300 mm to more than 1000 mm. The mean seasonal rainfall varies from 300 mm to 500 mm in summer (Kharif) and 250 mm to 300 mm in winter (Rabi). The dominant crops are wheat in the Rabi season; and sorghum and maize in the Kharif season depending upon the rainfall pattern. Crop calendar (two years two crops) is shown as figure 2. The general soil types consist of loamy eroded loess and shallow residual with some gulled lands. Outcrops of lime stones can also be found in the hilly areas. The land is partially cultivated while the rest is covered with thin and scattered vegetation.
Figure 1 Showing study area location
Figure 2 Cropping calendar on Pothwar area
(two years two crops)
