Assessing Groundwater Interactions between Forest and Crop Lands and the Potential to Increase Groundwater Availability through Afforestation in Mississippi

Author(s): Ouyang, Y.; Jin, W.; Feng, G.; Leininger, T.

Groundwater depletion due to agricultural pumpage in Mississippi has been an issue of increasing water resource concern. Currently, little to no effort has been devoted to estimating the impacts and potential benefits of afforestation on marginal agricultural lands for increasing groundwater availability. In this study, we modified the USGS’s MERAS (Mississippi Embayment Regional Aquifer Study) model to estimate such impacts and benefits in two different land uses at the Upper Yazoo River Watershed (UYRW) in Mississippi, one from crop land with groundwater pumpage and the other from forest land adjacent to the crop land. Three simulation scenarios were then developed for a simulation period of 147 years in this study. The first scenario was a base scenario for agricultural pumping conditions commonly used as well as natural forest conditions occurring in Mississippi. The second scenario was the same as the first scenario except that the model was iterated three times, respectively, at the increasing agricultural pumping rates of 5%, 10%, and 15% in crop land. The third scenario was the same as the first scenario except that the marginal crop land was converted to forest land a result of afforestation. These scenarios would ascertain: (1) the interactions of groundwater between the two land uses; (2) if groundwater from forest land is a source or is irrelevant to groundwater from crop land in Mississippi; and (3) the potential benefits of afforestation in marginal agricultural lands for increasing groundwater availability. Simulation results show that afforestation increased groundwater level by 3.3 ft after 27 years from 1980 to 2007 at the UYRW as a result of no groundwater pumpage in the afforested land. Our simulation further revealed that contribution of increasing groundwater recharge rate due to afforestation on groundwater availability at the UYRW was trivial. Further study is therefore warrant to estimate how afforestation of marginal crop land would enhance groundwater availability in the Lower Mississippi River Alluvial Valley.

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