Location Of Freshwater Research Articles

A robust definition of energy effectiveness for humidification dehumidification desalination systems

Humidification-dehumidification (HDH) is a cost-effective thermal desalination system that utilizes low-grade energy to extract freshwater from high salinity seawater with minimum maintenance. A robust method is presented using an innovative definition for energy effectiveness to facilitate the practical utilization of HDH modeling in the design process. This definition is mainly based on representing the flow stream on the temperature-enthalpy diagram to locate the pinch point and overcome the terminal-based definition limitation accordingly. The possible violation of the Second Law of Thermodynamics is the main drawback of the previous definitions due to the temperature-cross inside the humidifier, which defeats the purpose of air heating and humidification. The closed-air open-water HDH model is examined thermodynamically, and its design characteristics are explored at different operating conditions. The proposed definition is compared with analogous data from the literature. It showed an excellent agreement with a maximum discrepancy of 2.30%. Furthermore, a direct and straightforward design scheme is provided to estimate the dehumidifier and humidifier sizes based on the location and amount of freshwater needed. A case study for a system that produces 5 kg h−1 of freshwater in Dhahran is presented. The optimal energy effectiveness is found to be 78%, where the average minimum and maximum temperature of seawater in the system are assumed to be 25 and 70 °C, respectively.

On the Dynamics and Water Mass Transformation of a Boundary Current Connecting Alpha and Beta Oceans

AbstractA subpolar marginal sea, like the Nordic seas, is a transition zone between the temperature-stratified subtropics (the alpha ocean) and the salinity-stratified polar regions (the beta ocean). An inflow of Atlantic Water circulates these seas as a boundary current that is cooled and freshened downstream, eventually to outflow as Deep and Polar Water. Stratification in the boundary region is dominated by a thermocline over the continental slope and a halocline over the continental shelves, separating Atlantic Water from Deep and Polar Water, respectively. A conceptual model is introduced for the circulation and water mass transformation in a subpolar marginal sea to explore the potential interaction between the alpha and beta oceans. Freshwater input into the shelf regions has a slight strengthening effect on the Atlantic inflow, but more prominently impacts the water mass composition of the outflow. This impact of freshwater, characterized by enhancing Polar Water outflow and suppressing Deep Water outflow, is strongly determined by the source location of freshwater. Concretely, perturbations in upstream freshwater sources, like the Baltic freshwater outflow into the Nordic seas, have an order of magnitude larger potential to impact water mass transports than perturbations in downstream sources like the Arctic freshwater outflow. These boundary current dynamics are directly related to the qualitative stratification in transition zones and illustrate the interaction between the alpha and beta oceans.

Geophysical evidence for the hydro‐tectonic origin of the Sabkha El Sheikh Zwayed Lake and the shallow fresh water supplies, Northern Sinai, Egypt

ABSTRACTThe El Sheikh Zwayed Lake is a saline lake located in northern Sinai Peninsula. The origin of the lake as well as the shallow fresh water supplies between the lake and the Mediterranean are the subject of many geological, hydrogeological, and geophysical studies. Two main hypotheses have been sug gested to explain the phenomenon of the lake (i.e. hydrogeological and/or tectonic). Using direct current resistivity (DCR) and gravity data, we investigated which of these processes explain the jux taposition and the contradiction between the location of freshwater between the sea and a saline lake to the south which is supplied by a saline aquifer. We infer from the 1D and 2D resistivity inversions that a shallow grabenal structure exists between the lake and the coast. The gravity measurements enable a subsurface NE‐SW doubly plunging anticline to be suggested (and related to Syrian arc system) to the south‐west side of the lake as well as a NE‐SW associated deep inferred fault‐line crossing the lake. The results show that the hydrogeological regime in the study area is tectonically con trolled; whereby the graben structure works as a hydrogeological barrier between the lake and the sea.

Sensitivity of climate response to variations in freshwater hosing location

In a recent intercomparison of the response of general circulation models (GCMs) to high-latitude freshwater forcing (Stouffer et al., J Climate 19(8):1365–1387, 2006), a number of the GCMs investigated showed a localised warming response in the high-latitude North Atlantic, as opposed to the cooling that the other models showed. We investigated the causes for this warming by testing the sensitivity of the meridional overturning circulation (MOC) to variations in freshwater forcing location, and then analysing in detail the causes of the warming. By analysing results from experiments with HadCM3, we are able to show that the high-latitude warming is independent of the exact location of the additional freshwater in the North Atlantic or Arctic Ocean basin. Instead, the addition of freshwater changes the circulation in the sub-polar gyre, which leads to enhanced advection of warm, saline, sub-surface water into the Greenland–Iceland–Norwegian Sea despite the overall slowdown of the MOC. This sub-surface water is brought to the surface by convection, where it leads to a strong warming of the surface waters and the overlying atmosphere.

Microcomputer Applications of 1‐D Saltwater Intrusion Program

A one‐dimensional finite element program has been developed for use on the microcomputer as a study aid for students of groundwater hydrology. The program uses linear elements and the Galerkin weighted‐residual method to form the element matrix. A variety of boundary conditions can be applied. Unsteady problems can be studied, including sea‐level fluctuations and variations in recharge rates and pumping schedules. The aquifer can be confined or unconfined; the Ghyben‐Herzberg approximation can be specified or disregarded. The program can track as a function of time the location of freshwater and saltwater toes. Groundwater flow problems without any saltwater can also be studied. Students can use the program to learn several important concepts to groundwater flow and numerical analysis. These concepts include the effects of spatial discretization and time step on the stability and convergence of the program, parameter identification techniques, and sensitivity analyses.