Water quality parameter as a predictor of small watershed land cover

摘要

Different land cover affect water quality through interaction at root microsite during various phase of nutrient uptake. Litter layer and its decomposition, microbial interactions and physico-mechanical role to soil and water by vegetation influence directly or indirectly the draining water quality. However, the role of vegetation on water is dependent on scale of space and time. Water samples from creek and seepage were collected from mountainous catchment of varied land cover in southeastern Bangladesh to comprehend land cover effect in small catchment using paired watershed method. From the water sample analysis for common anions and cations, we revealed that water sample of shifting cultivated catchment contains higher SO42- and NO3- and lower HCO3-, Na+, K+ and TDS compared to natural vegetation area. The cations of water sample showed a regular trend than anions with land cover change in different sampling sites. Difference between creek and seepage water chemistry attributed to soil-water interaction during digging process associated to the shifting cultivation, plantation and agricultural landuse. Shifting cultivation and agriculture catchments exhibit higher NO3-N, SO42- total-phosphorous as well as base cations (Ca2+, Mg2+ and Na+) concentrations. From this study it revealed that anions such as SO42-, NO3-, Na+ and TDS are can be consistently use as an indicator water quality parameter to discern land cover change in this mountainous watershed. Monitoring of sensitive parameter would be effective to understand land cover change dynamics in a watershed. It was also sufficiently proved that the leaching of this ions in waterbodies from a landuse causing enrichment of the repository water body, where chemical fertilization is not seen being practiced for agriculture and forestry during the whole field campaign. The impacts of shifting cultivation and agricultural land uses on creek and seepage water chemistry are unlikely to lead to damaging consequences for the aquatic biota at present and in the near future in its current states and extends.