Stormwater ponds are intended to be used for mitigating floods, improving water quality, and recharging groundwater. The sediment-water interface (SWI) of stormwater ponds exhibits properties that influence surface water–groundwater exchanges similar to naturally occurring surface water bodies. However, these ponds are rarely monitored over time to account for their functionality. As organic and inorganic sediments accumulate on the pond bed, the ability of the SWI to conduct water is influenced by sediment deposition, accumulation, and compaction, as well as organic matter content and other biological processes. Two augmented methods, a sediment core permeability cell and an in situ aluminum tube and manometer, were evaluated for measuring the hydraulic conductivity of the SWI. The grain size, hydraulic conductivity, and percentage of organic matter were compared between two ponds constructed 22 years apart. Both methods were effective at measuring the hydraulic conductivities, especially in challenging encountered field situations, albeit with some shortcomings. The in situ method yielded data from sediments with low hydraulic conductivities due to thermal heating, expansion of the water, and the release of biogenic-derived gas from the sediments within the aluminum tube. The converted sediment core permeability cells generated the most consistent measurements. Grain size and hydraulic conductivities were correlated to pond age. The mean and effective grain sizes, as well as hydraulic conductivities of the older pond, were statistically lower than the younger pond in both shallow and deeper depths. Measurement of the changes in the SWI of stormwater ponds is important to protect urbanized areas from flood damage, control the quality and quantity of runoff, and maintain their groundwater recharge function.

Brackish to saline groundwater in arid environments encourages the development and sustainability of inland freshwater lenses (IFLs). While these freshwater resources supply much-needed drinking water throughout the Arabian Peninsula and other drylands, little is understood about their sustainability. This study presents a numerical model using the SEAWAT programming code (i.e., MODFLOW and the Modular Three-Dimensional Multispecies Transport Model (MT3DMS)) to simulate IFL transient evolution. The numerical model is based on a physical laboratory model and calibrated using results from simulations conducted in a previous study of the Raudhatain IFL in northern Kuwait. Data from three previously conducted physical model simulations were evaluated against the corresponding numerical model simulations. The hydraulic conductivities in the horizontal and vertical directions were successfully optimized to minimize the objective function of the numerical model simulations. The numerical model matched observed IFL water levels at four locations through time, as well as IFL thicknesses and lengths (R² = 0.89, 0.94, 0.85). Predicted lens degradation times corresponded to the observed lenses, which demonstrated the utility of numerical models and physical models to assess IFL geometry and position. Improved understanding of IFL dynamics provides water-resource exploration and development opportunities in drylands throughout the Arabian Peninsula and elsewhere with similar environmental settings.

Brackish water reverse osmosis (BWRO) desalination of groundwater is believed to be a sustainable method of providing municipal utilities with a high-quality supply in regions where freshwater sources are stressed and not sustainable. A key aspect of water management is the ability to evaluate an aquifer containing brackish water to ascertain future pumping-induced water quality changes and their impacts on the facility operation and economics. The city of Hialeah, Florida, has operated a BWRO facility for the last 9 years. The facility has a maximum design capacity of about 88,000 m³/d but is currently operating at about 33,000 m³/d. The facility was designed to treat water with a TDS of up to 10,000 mg/L. A detailed hydrogeologic investigation, including groundwater solute-transport modeling, suggested that the salinity of the source water would remain under 10,000 mg/L of TDS during the 30-year life expectancy of the facility. However, after 9 years of operation, it was found that the rate of salinity increase was much higher than predicted (27.5%), at the low rate of 33,000 m³/d. If the faculty was operated at the maximum capacity, the ability of the plant to treat the source water might be between 5 and 10 years. The conceptual model used to guide the solute transport modeling was not accurate for this site because it did not incorporate the apparent enhanced leakance through the basal confining unit below the aquifer. The greater leakance was likely caused by undetected, irregularly distributed fracturing of the underlying confining dolostones. The facility will require a major redesign to upgrade the process to be able to treat seawater at a TDS significantly above 10,000 mg/L in the future, should that occur. While the change will be costly, with a high capital cost to change the process, increased energy consumption, and overall higher water treatment cost, it is still more sustainable and has less environmental impact compared to other alternatives (e.g., treating tidal sources of seawater). The use of electricity from nuclear or solar generation could mitigate the environmental impacts of higher power consumption.