Trend analysis of the water quality of the tigris river using parametric and non-parametric tests

Water is an indispensable resource for the continuation of life. Although it covers a large part of the earth's surface, only 3% of it is freshwater and only 1% of this is available for human use. Global climate change is increasing the pressures on water resources and the need to manage water efficiently is becoming more and more important. In this context, monitoring and trend analysis of water quality play a critical role in the sustainable management of water resources. This study aims to determine the current status of water quality in the Tigris River and its tributaries and to examine the temporal changes in water quality parameters by nonparametric trend analysis. The Tigris River faces water quality problems especially due to pollutants from agriculture, industry and domestic wastes. Water samples taken in four different periods (March, June, September and December) between 2011 and 2020 were evaluated in terms of physical, chemical and biological parameters and statistical trend analyses were performed using Mann-Kendall test, Sen's Slope Estimator and Şen (2012) methods. The findings reveal that there are significant increasing and decreasing trends in some parameters of water quality. While increases were observed in parameters such as electrical conductivity (EC), total dissolved matter (TDS), chemical oxygen demand (COD), nitric nitrogen (NO₃--N) and ortho phosphate (O-PO₄3-), a decreasing trend was observed in dissolved oxygen (DO) levels. These changes were found to be directly related to the impact of agricultural fertilization, industrial and domestic wastes. In addition, a slight increase in pH levels was observed over the years, indicating a change in the alkalinity of the water. Monitoring these trends in water quality is of great importance not only for current water management but also for future water resources management and environmental sustainability. The findings show that changes in water quality can have impacts on hydrological structures, capacity calculations of water reservoirs and flood structures. Furthermore, monitoring changes in water quality will contribute to the protection of ecosystem health in the region. In conclusion, the changes in water quality in the Tigris River over time and their impacts on water management policies are critical for the conservation and sustainable management of water resources. Although the analyses show an increasing trend in water quality, a detailed examination of these trends and supporting them with larger data sets will be decisive for future water management and environmental sustainability. This study provides important findings to guide the development of sustainable water management strategies in water resource critical regions such as the Tigris basin.