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MIKE SHE is a physically based, integrated water resources model that simulates both surface and subsurface water dynamics. These dynamics include interception, evapotranspiration, overland flow, channel flow, unsaturated flow, and saturated zone flow. The model can also simulate limited surface water quality processes using the advection dispersion equation and groundwater quality with a random-walk tracking method. This article is intended to describe the components of MIKE SHE and its calibration, validation, and applications. Given the deterministic, physically based characteristics of MIKE SHE and the large number of processes it simulates simultaneously, the number of parameters to calibrate can be large. A combination of user experience with the model, knowledge of the problem being solved, and an automatic calibration feature help in selecting the most sensitive parameters to calibrate. A case study describing the use of the MIKE SHE model, coupled with the hydraulic MIKE 11 model, to solve water flow in agricultural reservoirs in south Florida is presented. The problem required the use of the MIKE SHE model due to the high groundwater and overland flow interactions as well as the complex flow patterns inside the reservoir. The horizontal and vertical saturated hydraulic conductivities and the leakage coefficient were identified as the calibration parameters. The model was calibrated and evaluated for two reservoirs using two different time periods. Results showed matching between measured and simulated data for both reservoirs for the calibration and validation periods. The coupled MIKE SHE/MIKE 11 model has the capabilities to simulate complex hydrological processes and their interactions, which few other watershed models can match, and is suitable for current problems, such as the effects of climate change and land use change. [ABSTRACT FROM AUTHOR]

The effects of organic amendments on vegetable crop production, phosphorus (P), and trace element (Zn, Cu, Mn, B, Cd, Pb, Ni) concentrations in groundwater were investigated on calcareous and sandy soils in south Florida. Treatments consisted of applying yard trash and food compost, biosolids compost, a co-compost of municipal solid waste and biosolids, and inorganic fertilizer. A randomized complete block design with four replications was used at both study sites. Total Kjeldahl phosphorus (TKP) and soluble reactive phosphorus (SRP) were periodically measured in grab samples collected for two years for both soils from wells above and below the spodic horizon at Ft. Pierce and from one depth at Homestead. Treatments were similar (P > 0.05) except on two sampling dates from the deep wells in the sandy soil at Ft. Pierce, one for SRP and one for TKP. Phosphorus concentrations for all treatments averaged < 1.2 mg SRP L-1 at Ft. Pierce and 0.04 mg SRP L-1 for the calcareous soil at Homestead. From solely a P consideration, organic P sources could be used to offset all or a portion of P required to satisfy vegetable crop nutrient requirements. This statement is consistent with crop yields at Ft. Pierce where yields from the three organic sources were equal to or exceeded inorganic fertilization yields. Micronutrient and trace element concentration responses to organic treatments were more pronounced at Ft. Pierce, perhaps due to soil chemical conditions including lower soil pH. The cocompost should be used cautiously to avoid contamination problems, especially when application rates are based on N fertilization as in this study. Due to the calcareous soil at Homestead, trace element concentrations in the groundwater were considerably lower than Ft. Pierce concentrations. However, the cocompost source was elevated for lead (Pb) (P < 0.05) compared with all other treatments, although higher concentrations were observed only on one sampling date. Results from this study indicated that, combined with the environmental benefits of recycling waste, the use of these organic amendments is a viable alternative to inorganic P fertilizers in the sandy and calcareous soils of peninsular Florida. The compost treatments were comparable to inorganic fertilizer with regard to P concentrations in the groundwater white producing similar or higher vegetable crop yields. [ABSTRACT FROM AUTHOR]

Experiments were conducted on calcareous and sandy soils to investigate the effects of organic amendments for vegetable production on groundwater nitrogen (N) concentration in south Florida. The treatments consisted of applying yard and food residuals compost, biosolids compost, a cocompost of the municipal solid waste and biosolids, and inorganic fertilizer. Nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), and total N concentrations were collected for a period of two years for both soils. Statistical analysis results revealed that for the three species tested, there were no significant differences among treatments. NO3-N concentrations for all treatments remained less than the maximum contamination level (10 mg/L). NO3-N transport to groundwater was higher in calcareous soil (mean=5.3 mg/L) than in sandy soil (mean=0.6 mg/L). NH4-N concentrations ranged from 0 to 13.6 mg/L throughout the experiment. Calcareous soil had lower NH4-N concentrations (mean=0.1 mg/L) than sandy soils (mean=0.7 mg/L). Total N ranged from 0.4 to 21.7 mg/L for all treatments for both soils reflecting high adsorption of dissolved organic N in both soils. Overall, results indicated that all the compost treatments were comparable to inorganic fertilizer with regard to N leaching and N concentrations in the groundwater while producing similar or higher yields. [ABSTRACT FROM AUTHOR]