Comparative assessment of water quality classification techniques in the largest north-western river of Cambodia (Sangker River-Tonle Sap Basin)

Abstract

The lack of adequate and good water quality is one of the serious issues that most developing countries are facing, yet environmental monitoring programs are not efficiently protecting ecosystem health. Here, we aimed to assess the suitability of different water quality assessment frameworks in order to define the most suitable method, especially for data-scarce environments, to quantify river ecosystem health. The study was conducted in the largest north-western river of Cambodia, the Sangker River in the Tonle Sap Lake (TSL) basin (UNESCO Biosphere Reserve). Five water quality assessment methods were selected for the study: Basic & Single Prati indices, Mekong River Commission water quality index (MRC-WQI), French water quality assessment system (SEQ-EAU) and US Environmental Protection Agency (US-EPA) framework. Overall, a physico-chemical gradient of water quality was observed along the river course. The river head was defined by high levels of dissolved oxygen (DO), low nutrients and chloride, while the middle course was marked by a gradual decrease of DO and increased concentration of nutrients up to the TSL floodplains. This degradation was explained by multiple impacts from human activities, e.g. domestic wastes, livestock, crop farming, causing simultaneous eutrophication and oxygen depletion along the river course. Despite those multiple pressures, the Sangker river health status was scored as fairly good reflecting the current situation of the river. So far, we found a convergence of the five water quality assessment methods; however, SEQ-EAU and Basic Prati seemed to be less suitable for tropical river health assessment. The study defined the US-EPA assessment method as the most suitable technique to quantify the Sangker river health. This method could potentially be used to monitor river ecosystem health in data-scarce environments. This would help overcome environmental monitoring challenges in developing countries faced by rapid global environmental changes.