Efficient use of water resources is one of the key goals of the National Cropping Pattern Plan. Achieving this requires accurate, region-specific economic valuation of water to help improve water pricing policies in agriculture. Mehran County, due to its shared border with Iraq and its advantage in exporting agricultural products (thanks to low transportation and storage costs), is an important case study for estimating the economic value of water in agriculture. In this study, field data were collected through interviews with 100 farmers in the region, using stratified sampling, during the 2023–2024 cropping year. The economic value of water for wheat, canola, barley, watermelon, tomato, and cucumber was estimated using parametric methods and production functions, including linear, Cobb–Douglas, and transcendental functions, under two scenarios: domestic consumption and export to Iraq. Based on econometric tests and classical assumption checks, the Cobb–Douglas production function was identified as the best fit. The results showed that the economic value of each cubic meter of water in the domestic consumption scenario was 21, 61.142, 17.139, 59.899, 27.124, and 37.219 thousand rials for wheat, canola, barley, watermelon, tomato, and cucumber, respectively. Under the export-to-Iraq scenario, these values were 0.036, 0.064, 0.054, 0.166, 0.1211, and 0.087 USD, respectively. The findings highlight the need to adjust the cropping pattern in this region—specifically, to increase the cultivated area and production of crops with higher economic water value (canola, watermelon, cucumber for domestic consumption; watermelon, tomato, cucumber for export)—and to reform water pricing policies in agriculture. This includes gradually increasing the water fees paid by farmers so that the price of water approaches its economic value, thereby strengthening the National Cropping Pattern Plan and promoting efficient water use in agriculture.