Assessing temporal-spatial variations and classifying water quality of the Dinachal River, Iran, through field data collection

Document Type : Research Paper

Authors

• Sina Asadpour lomer ¹
• Kumars Ebrahimi ²
• Abdolmajid Liaghat ¹
• Fatemeh Alipour ²

¹ Irrigation and Reclamation Engineering Department, Agricultural Faculty, University of Tehran, Karaj, Iran.

² Professor, Department of Renewable Energies and Sustainable Resources Engineering, Faculty of New Sciences and Technologies, University of Tehran, Tehran, IRAN.

Abstract

Keywords

• Guilan
• Pollution
• Sustainable exploitation
• Surface water resources
• Water quality

Main Subjects

• منابع آب

Assessing temporal-spatial variations and classifying water quality of the Dinachal River, Iran, through field data collection

EXTENDED ABSTRACT

Introduction

The monitoring and assessment of water quality in rivers play a pivotal role in understanding the dynamics of aquatic ecosystems and their interactions with anthropogenic activities. The Dinachal River, located in Gilan Province, serves as a vital water source for both natural habitats and human utilization. Water quality, a key determinant of the river's ecological health and its suitability for various purposes, is subject to complex temporal and spatial variations influenced by a myriad of factors. The aim of the present article is to monitor the temporal and spatial quality of water in the Dinachal River in Gilan Province, based on field studies, sampling, and laboratory experiments.

Materials and Methods

The Dinachal River, coursing through the Gilan Province of Iran, was chosen as the focal point of this study due to its ecological significance and human dependency. The river's diverse catchment area, characterized by a blend of agricultural, residential, and industrial activities, provides a rich context for examining the intricate relationships between land use practices and water quality dynamics. To monitor the water quality of this river, five hydraulic parameters and thirteen water quality parameters such as nitrates, phosphates, temperature, and acidity were measured and studied at seven selected sections along a 25-kilometer stretch of the river. The test results are presented for use by other researchers in this article. For spatial monitoring, the variations in water quality parameters from upstream to downstream were compared, and for temporal monitoring, the data from research conducted in 2012 were compared with the data obtained from field visits. To analyze the results, many diagrams and indices such as Schuler, Piper, Wilcox diagrams, as well as FAO and WQI indices were used.

Results

The results of the spatial comparison of river water quality indicate that the values of most parameters, including phosphorus, sodium, calcium, and potassium, gradually increased from upstream to downstream, with a relatively constant slope, but experienced a sharper increase from section 4 onwards. Among these parameters, electrical conductivity, nitrate, and total dissolved solids have shown significant increases across the examined stretch. Specifically, the electrical conductivity has increased from 315.67 µS/cm to 712 µS/cm, total dissolved solids have increased from 202.03 mg/l to 455.68 mg/l, and nitrate concentration has increased from 11.27 mg/l to 69.47 mg/l. However, the acidity parameter, in contrast to the others, exhibited only a minor change, increasing from 7.75 to 7.82, whereas the dissolved oxygen experienced a reduction from 7.68 mg/l to 4.99 mg/l. Furthermore, the results of the temporal comparison of river water quality demonstrate that the dissolved oxygen content has experienced a negligible decrease of approximately 8%, while nitrate concentration has increased from 19.4 mg/l to 21.4 mg/l, and electrical conductivity has increased from 328 µS/cm to 416 µS/cm, when compared to the past. Notably, the acidity parameter has shown no substantial variation from the past, decreasing from 7.91 to 7.81. Based on comparisons spanning from 1996 to 2016, encompassing the months of June to July, it is evident that due to the inflow of agricultural runoff, nitrate levels have exceeded permissible limits. Nonetheless, when examinations were conducted in September 2021, marked by the absence of agricultural activities, the nitrate conditions along the entire river, except for the final segment, exhibited stability.

Conclusion

 In conclusion, this study underscores the crucial significance of monitoring and comprehending the temporal and spatial dynamics of water quality in the Dinachal River within Gilan Province. The results pinpoint variations in numerous parameters, illuminating the impact of agricultural activities and other factors on water quality. These findings underscore the necessity of sustainable resource management strategies to maintain the health and usability of surface water resources in the region.