STUDI LINGKUNGAN FISIK DI KAWASAN SUB DAERAH ALIRAN SUNGAI GARANG

Physical Environment Study in Sub Garang Watershed

Abstract

Sub watershed  is a dynamic ecosystem  with an interdependent  among components.  When  a watershed experiences an overload canying  capacity situation  caused by the heavy human activities, the environment's damage will happen especially inphysical and chemical character, land productivity, and the occurrence   of flood and draught.  All of these, will affect the environment  sustainability.

This study's objective  is to learn  the physical changes of garang sub-watershed  in Semarang, related  to erosion,  flood, and draught  in this  area. Method used is field survey, to identify  the erosion level and flodd level, and to measure  the draught  level. Parameter  employed  are; rainfall's erosion, land erosion  factors, length abd slope level, and management   factors of vegetation  and erosion. To study the flood factors, parameter used are :  rainfalls,  volume  and surface  water  level, and maximal and minimal  debit of water. The drought  factors used for parameter are :  rainfalls,  width  index  of leaves, crop/vegetation co efficient,  actual evapotranspiration, and crop's evapotranspiration. Analyses method used for measuring the erosion level is USLE  method, while for the flood level is letting curb method, and for draught level is'SARRA   method.

The results show that the actual erosion of garang sub-watershed  is between  0.932 ton/ha/year to 1.680.532  ton/ha/year. The flood curb in the catchment's  area has commodities  is between    0.61 to 0.94.