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Development and evaluation of the Maxey-Eakin recharge method

Stephens, Daniel B., Umstot, Todd
Hydrogeology journal 2019 v.27 no.2 pp. 747-760
atmospheric precipitation, basins, groundwater recharge, phreatophytes, valleys, Nevada
The Maxey-Eakin method affords a convenient means to estimate natural groundwater recharge and has been widely applied to desert basins in the Southwestern United States. The method relies simply on recharge percentages applied to volumes of precipitation within a basin, with recharge percentage increasing with precipitation. It has been presumed that the method was developed for closed desert basins, where recharge equals natural discharge. The recharge coefficients were derived through a trial-and-error process using an annual precipitation map of Nevada dated 1936, applied to natural discharge by phreatophytes in 13 valleys in Nevada. Details of the derivation have not been published and have not been reproduced by anyone. The identity of the valleys used in the derivation cannot be confirmed. The 1936 precipitation data likely underestimated the mean annual precipitation, and field measurements indicate that the estimates of natural discharge by phreatophytes were also underestimated. Nevertheless, the method has been extensively utilized, even outside Nevada, apparently with good results. The wide applicability of the recharge coefficients may be attributed more to the excellent professional judgment of the developers than to the trial-and-error process that relied on phreatophyte uptake and the 1936 precipitation map of Nevada.