EFFECTS OF SELECTIVE LOGGING METHODS ON WATER YIELD AND STREAMFLOW PARAMETERS IN PENINSULAR MALAYSIA

Abstract

An experimental forest watershed, consisting of three small catchments at Berembun Forest Reserve, Negri Sembilan in Peninsular Malaysia was monitored from 1979 to 1987. Adequate instruments were installed for continuous collection of hydrologic and climatic data. The calibration and post-treatment phases lasted for three and four years respectively. Two types of treatments were imposed, namely, commercial selective logging and supervised selective logging in Catchment 1 and Catchment 3 respectively, while Catchment 2 remained as a control. Pertinent logging guidelines were prescribed and assessed in Catchment 3 in terms of hydrologic responses. Significant water yield increases were observed after forest treatment in both catchments amounling to 165 mm (70%) and 87 mm (37%) respectively in the first year; increases persistently till the fourth year. Magnitude and rate of water yield increase primarily depended on the amount of forest removed and the prevailing rainfall regime and the increase was largely associated with baseflow augmentation. Conservation measures introduced in this study - the use of buffer strips, cross drains, an appropriate percentage for the forest road network-were found to be effective and beneficial in ameliorating the hydrological impacts