Sustainable Water Management in the Kelani River Basin

The study is concentrated on the present water pollution and future challenges of water usage in downstream of Kelani River. The river section between Avissawella to Ambathale was focused in the study. The study was implemented in two parts. The part one is investigation of water quality distribution and the future situations over the river using QUAL2k water quality modeling software. The secondary data collected from NWSDB was used to model calibration and validation. The finalized model was used to simulate water quality distribution under different flow conditions. The simulations were focused on dry weather period flow conditions as it is the most strained period of the year. As per the results, increased demand projected for the future itself is under risk of alarming pollutions. The increased demand coupled with further pollutant loading to the river leads to accelerate degradation of water quality in Kelani River. The conditions may escalate to risk the human usage of river water and drinking water supply due to exceeding tolerance limits of raw water unless pollution is mitigated with sustainable utilization to meet future demand. Under the second part, domestic end user consumption in service area was measured using direct measurement to investigate the end user consumption volumes of household. It is noted through the study that 15–30% of domestic water consumption could be replaced with alternative water sources. This will reduce the future extraction by 10–35% in downstream of Kelani River and decrease the risk for disturbing pollution. Utilization of alternative water sources also saves millions of rupees required for investing water supply infrastructures and subsequent operation and maintenance facilities.