Assessment of hydrogeochemical characteristics of groundwater in space and time is crucial in arid areas where limited groundwater resources have been overexploited for socioeconomic development. This study investigates governing hydrogeochemical processes and spatiotemporal evolution of groundwater hydrochemistry utilizing long-term (1986-2019) hydrochemical data of groundwater of Umm Gudair groundwater field following geostatistical and isotope techniques. Ion exchange, dissolution of evaporites, weathering of silicates and dissolution of carbonates were governing hydrogeochemical processes. Temporal trend analyses for a period of 34 years of hydrochemical parameter data revealed the presence of six trends:1) stable, 2) no trend, 3) probably decreasing, 4) decreasing, 5) probably increasing and 6) increasing with the dominance of trends 1 to 4, indicating an overall improvement in groundwater quality due to the influx of high-quality groundwater from the recharge area. The groundwater exploitation has resulted in variation of groundwater flow manifested by drop in water level and thus extraction promotes the flow of high-quality water from the recharge area. Spatial interpolation of hydrochemical parameters revealed an increase in magnesium, potassium, sulfate, and boron concentrations while decreasing pH, electrical conductivity, total dissolved solids, sodium, chloride, bicarbonate, nitrate, silica, and fluoride. Magnesium, sulfate and boron concentrations were found to be sensitive to groundwater production volume and drawdown. Their concentrations increased with increase in groundwater production volume and drawdown, implying that groundwater quality can be regulated through adjustment in groundwater production and drawdown.