Effect of Land Use Type on Water Quality in the Lam Phachi Sub-watershed

Abstract

This research aimed to study the effects of agricultural and forested land using on the level of water quality at the Lam Phachi sub-watershed.  Eight water quality parameters were collected and analyzed during both wet and dry periods in 2018 and were compared with the surface water quality standard. Additionally, the water quality was determined by comparing with the Water Quality Index (WQI). From the results, it was found that temperature, pH, DO, nitrate, and phosphate content of the forested sub-watershed, agricultural sub-watershed and outlet of Lam Phachi sub-watershed were at the second typed of the surface water standard during both the wet and dry periods. However, the Biochemical Oxygen Demand (BOD) of agricultural sub-watershed and total coliform bacteria of the outlet were higher than the surface water standard during the wet period. Moreover, the total suspended sediment in the agricultural sub-watershed and outlet, during the wet period, was greater than of the forested sub-watershed. Water quality assessment through the water quality index (WQI) indicated that water quality of the forested sub-watershed was at an acceptable level during both the wet and dry periods, but that in the agricultural sub-watershed and outlet was poor during the wet period and slightly better during the dry period. It can be concluded that agricultural land use in the Lam Phachi sub-watershed has affected the suspended sediment and BOD levels. Hence, soil and water conservation should be managed accordingly to reduce surface runoff and soil erosion in the sub-watershed.