Analyzing the Sustainability and Trend of the Depth to Groundwater in Mazandaran Province

The permanent exploitation of groundwater requires adopting appropriate policies for the quantitative and qualitative protection of this valuable resource. Considering the reliance of a part of the development plans of Mazandaran province on groundwater, in this research, the sustainability and trend of groundwater depth (GWD) changes were investigated in the 1991 to 2020 period (1991 to 2000: first decade, 2001 to 2010: second decade, 2011-2020: third decade). Mann-Kendall test and Sen’s slope estimator were used for trend analysis. Groundwater sustainability was assessed using four indicators including, renewable groundwater per capita (GWRRp), total abstraction of groundwater/groundwater recharge (TAGR), total abstraction of groundwater/exploitation of groundwater resource (TAGE), and water exploitation index (WEI). The values of the Man-Kendall statistic ranged from -2.50 to 3.76, indicating the increasing trend of GWD during the last 30 years in all areas except Babol-Amol (second and third decades) and Noor-Nooshahr (third decade). During the first and second decades, the amount of GWD in Mazandaran province increased by 0.21 and 0.12 meters per year, respectively. According to GWRRP, TAGR, and TAGE indicators, the west of Mazandaran had better conditions than the central and eastern regions of the province. Based on the WEI indicator, Ramsar-Chalous and Noor-Nooshahr areas (WEI<10), Behshahr-Bandargaz, Babol-Amol and Sari-Neka areas (10<WEI<20), and Qaemshahr-Joybar area (WEI>20) were in a satisfactory, worrying and critical condition, respectively. Based on the results, the groundwater situation in a large part of Mazandaran is unsustainable and requires the adoption of appropriate management strategies to prevent the increase in this unsustainability.