Land use development strategies for the rehabilitation of Gadjahmungkur reservoir subwatershed

Abstract

A land use planning study was conducted for Upper Solo, G4jahmungkur Reservoir subwatershed to determine the best land use alternative through simulation models to obtain least erosion _rate, well distributed streamflow, increased crops productivity and improved incomes of farmers. A PC-based ARC/INFO version 3.4 D-Plus was used in the analysis and processing of the data to generate spatial simulation models of the subwatershed land use. The Univer­sal Soil Loss Equation (OSLE) was used as the basic method for all computations. The ratios of maximum and minimum discharge and runoff coefficients from 1982 until 1993 were observed to have no trend. The stream discharge and sediment load before and after 1988 were somewhat erratic. The present erosion rates ranged from 1.01 to 3,343.40 mt/ha/year in the different land mapping units, the average being 159.47 mt/ha/year or about 15.95 mm/year, higher than the tolerable soil loss (TSL) of 30.03 mt/ha/year or about 3.0 mm/year. The critical erosion areas are settlements and home gardens, unpaved roads ditches and trails. Results of the simulation models indicate land use alternative 4 as the best option. Land use alternative 4