Assessing the Relationship Between Electrical Conductivity and Total Dissolved Solids of Different Water Resources in a Large-scale Irrigation Scheme in the Eastern Mediterranean Basin of Turkiye

Climate change and the growth of the population have led to changes in both the quantity and the quality of water resources. In Turkiye, a Mediterranean country, over 75% of its surface water is used for irrigation. Given the average annual precipitation (574 mm) of Turkiye, except for the Black Sea Region, all arable land in the country relies on irrigation to maintain sustainable food production. Agriculture constitutes 6% of Turkiye’s gross domestic product (GDP), with exports including crops such as cotton, corn, cereals, pulses, oilseeds, nuts, citrus orchards, and various fruits. As a result, the water provided for irrigation in any irrigation system must meet acceptable water quality standards to ensure sustainability of irrigation and food security. This study aims to a) investigate two essential irrigation water parameters: Electrical Conductivity (EC) and Total Dissolved Solids (TDS), and b) evaluate their empirical relationship using samples collected from various water sources within a large-scale irrigation district, covering an area of 9495 ha in the Eastern Mediterranean Region of Turkiye. Water samples were collected over one year, from October 2022 to September 2023. A total of thirteen locations were considered: a) Seven agricultural drainage channels, b) Four irrigation water sources (Seyhan River, Ceyhan River, one spring, and one groundwater well), c) Two outlets - the existing research catchment outlet and the other downstream. EC values of water samples were determined by using a benchtop type EC meter in the laboratory and TDS was determined by gravimetric method. Research results showed that there was a statistically significant correlation (r≥0.98) between EC and TDS across all water samples. The proportionality constant (K) ranged predominantly between 400-800 and was consistent with literature indicating the linear relationship between EC and TDS. Research findings suggest that the quality of different water supplies is suitable for the irrigation of all kinds of crops grown in the Lower Seyhan Plain of Turkiye. The overall characteristics of the average EC and TDS values throughout the year are reflected in the proposed equations for each water body. However, in future research, we suggest that the water sample volume should be at least 100 ml in order to provide more accurate results for water quality assessment.