Çitgez, TarıkKaragül, RefikÖzcan, MehmetÖzbayram, Ali Kemal2023-07-262023-07-2620222602-4039https://doi.org/10.5152/forestist.2021.20054https://search.trdizin.gov.tr/yayin/detay/521124https://hdl.handle.net/20.500.12684/12871This study was carried out in two watersheds of the Big Melen Stream, which provides water to Istanbul. Forest areas are dominant in the Yukarikarakoy 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), NO2-, NO3-, SO42-, PO43-, and NH4+ 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, NO3-, SO42-, and DO of the sampling point representing the forest were 264 mu S/cm, 1.5 mg/L, 3.1 mg/L, 14.7 mg/L, and 10.3 mg/L, respectively. The mean EC, TN, NO3-, and SO42- values of the point representing the hazelnut plantation were higher than those of the point representing the forest. In the sampling points representing the settlement areas of both watersheds, the EC and PO43- increased, while the DO decreased. As a result, it was determined that the stream water of the point representing 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.en10.5152/forestist.2021.20054info:eu-repo/semantics/openAccessBig Melen Stream; Land Use Type; Nonpoint-Source Pollution; Water Quality ParametersRiver; Urban; Variability; Hydrology; Impacts; Turkey; BasinArticle72173805211242-s2.0-85125927171WOS:000742149500008Q4N/A