Effect of Land Use on Some Physical and Chemical Water Quality Parameters in the Sub-watersheds of Big Melen Stream

Abstract

This study was carried out in two watersheds of the Big Melen Stream, which provides water to Istanbul. Forest areas are dominant in the Yukarıkaraköy watershed, whereas agricultural areas (hazelnut plantations) are dominant in the Avlayan watershed. There are settlement areas at the outlet regions of both watersheds. The purpose of the study was to compare the effect on the water quality as a consequence of the forests, settlement areas, and hazelnut plantations. Accordingly, pH, electrical conductivity (EC), dissolved oxygen (DO), total nitrogen (TN), NO 2 − , NO 3 − , SO 42 − , PO 43 − and NH 4+ concentrations were measured in the stream points representing hazelnut plantations, forests, and settlement areas for 2 years. The water quality classification of the sampling points was determined in accordance with the criteria specified in the Turkish Surface Water Quality Regulations (SWQR). The mean EC, TN, NO 3 − , SO 42 − , and DO of the sampling point representing the forest were 264 µS/cm, 1.5 mg/L, 3.1 mg/L, 14.7 mg/L, and 10.3 mg/L, respectively. The mean EC, TN, NO 3 − , and SO 42 − values of the point representing the hazelnut plantation were higher than those of the point repre- senting the forest. In the sampling points representing the settlement areas of both watersheds, the EC and PO 43 − increased, while the DO decreased. As a result, it was determined that the stream water of the point rep- resenting the forest was of higher quality than that of the point representing the hazelnut plantation and that the settlement areas significantly reduced the water quality by increasing the concentrations of pollutants. This study was carried out in two adjacent sub-watersheds of Big Melen Approximately 64% (214 ha) of the Yukarıkaraköy watershed is forest and 36% (120 ha) agricultural land, whereas 27% (194) of the Avlayan watershed is forest, 70% (499 ha) agricultural land, and 3% (21 ha) settlement. Most of the agricultural land in the watersheds is used for hazelnut cultiva-tion, and the usage of fertilizers is common in these areas.