Document Type : Research Paper

Authors

• Fariba Karami ¹
• majid ranjbari ²

¹ Academic Sttaf

² The Secretary of education training

Abstract

The rivers are the most important supplies of fresh and agricultural water in the cities and villages. The importance of chemical quality of waters is becoming increasingly important due to the increase and diversity of Anthropogenic activities in the urban and rural environments. Therefore, the current study aimed to investigate the trend of land use changes and the chemical quality of surface water in a period of twenty years in the Qaranquchai River in Hashtrud Ccounty. The Qaranquchai is one of the sub-basins of Qezel Ozen River in the northwest of the country. In this research, Land use maps for the years 2021 and 2001 were prepared and drawn using Sentinel 2 and Landsat 7 satellite images, and were examined their changes. The chemical quality data of surface water in the hydrometric stations of the Qaranquchai basin, including Mg, Ca, EC, TDS, Cl, HCO, SO4, K and Na were obtained from the Regional Water Organization of East Azarbaijan province from 2000 to 2020. Then, their changes over 20 years were analyzed using the Mann-Kendall test. The results of the analysis of land use changes showed that in 2001, the largest area of land use was pasture, while in 2021, rainfed land had the largest area in the Qaranquchai basin. In fact, during the studied years, with the increase of rainfed agricultural land from 38% to 53.1%, pasture land decreased from 60.17% to 42.3%. The results of the investigation of the changes of the chemical quality indicators of the water in the hydrometric stations in the Qarangochai river in the studied time period, showed that the trend of changes was increasing. The result of the increasing process of each of the anions and cations in the river water has caused its quality to decrease.

Highlights

In the analysis of the chemical quality of the river water over twenty years, the examination of the trend of changes in the index of Total Dissolved Solids (TDS) tested by the Mann-Kendall test showed that the monthly trend of changes has been significant and increasing in each time series, except for May and June. Also, seasonal studies show that despite the increasing and positive trend of TDS changes in the spring and summer, there is a relatively balanced linear trend (Sen's slope) in the autumn and winter. Examining the trend of changes in sulfate index (SO4) showed that its change trend in the spring, summer, and autumn for the period of 2000-2020 was insignificant; however, in the winter, it was higher than the alpha level of 0.05% of the mean trend with a value of 0.559.

Furthermore, in terms of the regression trend line or the Sen's slope, except for the winter, there has been a significant increase and positive trend for the rest of the year. Examining the trend of changes in Sodium Absorption Ratio (SAR) shows that the trend of the data in most months of the year except January has had a positive and significant trend. The seasonal and annual changes are also the same. Also, the regression trend line (Sen's slope) has been increasing.

Conclusion:

The Qaranquchai basin is one of the important basins in the country's northwestern region, whose water is used for agriculture and drinking. According to the results of the current study, it can be seen that the trend of water's chemical quality reduction in the Qaranquchai River. The results show that the changes of important indicators in the study area, including potassium (k), magnesium (Mg), sodium (Na), chlorine (Cl), electrical conductivity (Ec), water-soluble solids (TDS) and sulfate ( So4) the trend of data changes in monthly, seasonal and annual time series has extreme fluctuations and abnormal changes. It seems that the reason for these extreme changes and fluctuations in these time series can be related to the climatic factors of the studied basin and changes in land use, as well as the activities of some industries and even mines and the existence of urban and rural population centers in different parts of The study area should be related.

Key word: Chemical quality of water, Mann Kendall test, Qaranquchai River

Keywords

• Land use
• Hydrochemistry of water
• non-parametric tests
• Qaranquchai basin

Main Subjects

• Geomorphology