Changes In Water Demand Research Articles

Adequacy of Surface Water‐Supply Systems: Case Study

Water‐supply planners and managers must continually evaluate the ability of surface water sources to meet current and future demands of public water‐supply systems they serve. Water demand changes over time, increasing with population growth and industrial development. However, continuing sedimentation in surface water reservoirs reduces their capacities and expected future yields. A method has been developed to calculate future reservoir capacity losses due to the sedimentation process. The method allows for consolidation or compaction of sediment constituents with time. Mitigatory measures for increasing the availability of water to deficient systems are investigated. These measures for maintaining adequate, reliable water supplies are devised to achieve optimal use of water resources with minimal adverse impacts on stream and riverine ecology. All surface water‐supply systems in Illinois are investigated with respect to their future demands, yields of their water sources, any present and future inadequacies for specified drought frequencies, and feasible and economical mitigatory measures.

RISING GROUNDWATER LEVELS IN THE UNITED KINGDOM.

Over recent years, rising water-table levels have been reported in a number of major cities throughout the world. In Britain, the most well-known examples are in London, Birmingham and Liverpool, but similar conditions have been experienced in some other cities and industrial areas. A common cause for these cases of rising water-tables is changing water demands by industry, which results in a reduced abstraction from their private sources. There is some evidence that leakage from water mains and sewers is also significant in some areas. Changes in the pattern of direct groundwater abstraction by industry have been reviewed and compared with case histories revealed by a survey of the regional water authorities in England and Wales. Outline details of examples in Britain have been collated, together with a few case histories from other countries.

Water‐Balance Calculations for Solid‐Polymer‐Electrolyte Fuel Cells

The proper balance between water production and removal is particularly important for successfully operating solid‐polymer‐electrolyte fuel cells. Imbalance between production and evaporation rates can result in either flooding of the electrodes or membrane dehydration, both of which severely limit performance. We present a mathematical model of the solid‐polymer‐electrolyte fuel cell that identifies operating conditions that result in a water balance. The model is one‐dimensional and is derived from basic principles of gas‐phase transport. The mechanisms of membrane water transport are not included explicitly in the model, and the membrane is taken as uniformly wetted, which renders the model most applicable to thin membranes. We suggest how humidification of reactant gases can be adjusted as current density is varied during an experiment (at constant temperature, pressure, and reactant feed rates) in order to accommodate the fuel cell's changing demands for water. Humidification requirements of inlet reactant gases for a wide range of practical operating temperatures, pressures, and gas feed rates have been identified. The analysis also identifies conditions in which reactant transport limitations govern the behavior of the fuel cell.