Effects of Land Use on Spatial-Temporal Variation of Ground Water Quality (Case Study: Mashhad plain)

Modeling the spatial-temporal variation of water quality and analyzing the effects of land use changes on the qualitative parameters of groundwater is very important. In this research, the ability of various deterministic and geostatistical techniques in the prediction of spatial-temporal qualitative parameters regarding drinking, agriculture usages and effects of infiltration rate of water into the soil  in Mashhad’s plain were investigated by using statistical data of 62 observation well from 1996 to 2016. The land use maps were prepared by ENVI5.1 using Landsat images. Analysis of isoline maps showed that the water quality had been dropped considerably in terms of chlorine and total hardness and the area with class of sever restricted usage had been increased. Investigation of EC isoline maps showed that in the year 2016, the area of regions with moderate and sever restricted usage was the highest in comparison to 1996 and 1986. The pH isoline maps showed that the major part of study area is located in the moderate restricted class. According to SAR isoline maps, all part of the study area is located in non-restricted class and it has approximately remained constant during the years. The geological maps of study area showed that the formations have good effects on groundwater quality. Analysis of Land use maps showed that rangeland and agriculture have received the most area of land use.  During the studied period, rangeland and agriculture had the most decrease (6.61 %) and increase (2.16%) equivalent to 643.29 and 235.46 square kilometer, respectively. By moving from center to northeast part of Mashhad’s plain, the agricultural lands and the number of illegal wells and urban industrial land use is increased which altogether have led to the significant loss of water quality.