Effects of Land Cover Change on the Energy and Water Balance of the Mississippi River Basin

The effects of land cover change on the energy and water balance of the Mississippi River basin are analyzed using the Integrated Biosphere Simulator (IBIS) model. Results of a simulated conversion from complete forest cover to crop cover over a single model grid cell show that annual average net radiation and evapotranspiration decrease, while total runoff increases. The opposite effects are found when complete grass cover is replaced with crop cover. Basinwide energy and water balance changes are then analyzed after simulated land cover change from potential vegetation to the current cover (natural vegetation and crops). In general, net radiation decreases over crops converted from forest and increases over crops converted from grasslands. Evapotranspiration rates decrease over summer crops (corn and soybean) converted from forest and increase over summer crops converted from grassland. The largest decreases (∼0.75 mm day−1; 20%) are found in summer over former forests, and the largest increases (∼0.4 mm day−1; 45%) are found in spring over former northern grasslands. Drainage rates increase over summer crops converted from savanna and forest and decrease over summer crops converted from grasslands. The largest increases (∼0.6 mm day−1; 45%) are found in winter over summer crops in former southern forests, and the largest decreases (∼0.4 mm day−1; 25%) are found in summer over summer crops grown in former northern grasslands. The simulated energy and water balance changes resulting from land cover change depend on season, crop type (winter, spring, or summer plantings) and management, and the type of natural vegetation that is removed.