Priority ranking of Skudai River sub-watersheds for potential flood damages and water quality parameters

Abstract

Sustainability of a watershed generally depends on climatic, hydrological, environmental, social, economical, ecological and many more other factors. The watersheds in Malaysia generally have two issues, which are water quality degradation and flash floods. Economic development activities have increased many folds in last few decades which have affected many watersheds including Skudai River watershed. In this study, Skudai River watershed was delineated into 25 sub-watersheds (SW) and a sustainability index for the watershed was developed by considering Potential Water Quality Deterioration (PWQD) and Potential Flood Damage (PFD) parameters. In order to get actual or at least close to actual classification of river water, the existing water quality index (WQI) developed by the Department of Environment (DOE) known as DOE-WQI formula was modified by adding six more important water quality parameters, which were total phosphorus, nitrate, total dissolved solids, electrical conductivity, turbidity and temperature. The weights to the water quality parameters in the modified WQI were elicited from 32 water experts in face-to-face survey. The modified WQI produced river water classifications, which were Class II for Skudai River- Natural (SKN) and Skudai River- Head (SKH) sampling points and Class III for Senai River (SEN), Skudai River- Middle (SKM), Skudai River- Tail (SKT), Danga River (DAN), Melana River (MEL) and Kempas River (KEM) sampling points. The weights of watershed sustainability indicators in the Skudai River watershed sustainability index (WSI) were obtained from 30 stakeholders consisted of engineers from various departments. Combining modified WQI and PFD parameters using pressure-state-response (PSR) model resulted in a framework of WSI for the Skudai River watershed. The WSI score for every sub-watershed was calculated by incorporating watershed sustainability indicators data and weights. The final ranking of sub-watersheds was SW2> SW7> SW6> SW1> SW4> SW3> SW5> SW8> SW12> SW18> SW25> SW10 >SW9 > SW14> SW16> SW24> SW17> SW11> SW22> SW19> SW13> SW15> SW21> SW23> SW20.