Rangeland Degredation and Its Impacts on Water Quality in Zayandehroud River Basin

Abstract

The quality of water in many regions of world are threatened by overuse, misuse and pollution, and it is increasingly recognized that water quality of rivers, streams and wetlands are strongly influenced by landscape characteristics of their watershed including landscape composition (i.e. land use/land cover types and their fractions) in uplands and the spatial configuration of these land use/land cover types. This study focuses on the effects of land cover changes on the water quality of Zayandehroud River. The main goal of this study was to quantify the change in rangelands and forests in Zayandehroud river basin, which suffered intense human interference, in a period of eleven years (1997–2008) and to evaluate how landscape patterns (including Number of Patches, Edge Density, Percentage of Rangelands and Forests) influence on the water quality indices (including BOD5, EC, NO3, P and TDS) measured in 10 stations along the Zayandehroud river. The results indicated that water quality were significantly correlated with both the proportions and configuration of Rangeland areas. Total edge of range land area had positive effects on water quality, especially on BOD 5 and EC. The proportion of rangeland was negatively correlated with water quality variables. Also PLAND and LPI metrics of range land had positive effect on decreasing nutrient (NO 3 , PO 4) of water in this river. However, there was no significant correlation between water quality variables and proportion of Forest in Zayandehroud basin. Because Zayandehroud basin is located in a semi-arid area, where forests are very limited and are occurred only in small patches with low density. It was shown that degradation of range land lead in to degradation of water quality which highlights the importance of rangeland conservation in water quality management at landscape scale.