Sustainable yield of ground water. All groundwater pumping comes from capture; the greater the intensity of pumping, the greater the capture. Capture comes from decreases in natural discharge and increases in recharge. Natural discharge supports riparian, wetland, and other groundwater-dependent ecosystems, as well as the baseflow of streams and rivers. Capture depends on usage, and it is not related to size or hydrogeological characteristics of the aquifer, or to the natural recharge. The traditional concept of safe yield, which equates safe yield with natural recharge, is flawed and has been widely discredited. It has now been replaced with sustainable yield. Sustainable yield depends on the amount of capture, and whether this amount can be accepted as a reasonable compromise between a policy of little or no use, on one extreme, and the sequestration of all natural discharge, on the other extreme. A reasonably conservative estimate of sustainable yield would take all or suitable fractions of deep percolation. On a global basis, deep percolation is about 2% of precipitation. Sustainable yield may also be expressed as a percentage of recharge. Limited experience suggests that average percentages may be around 40%, with the least conservative around 70%, and reasonably conservative around 10%. Sustainability may be fostered by enlightened management which seeks to capture rejected recharge, encourage clean artificial recharge, and limit negative artificial recharge. A holistic approach to groundwater sustainability considers the hydrological, ecological, socioeconomic, technological, cultural, institutional and legal aspects of groundwater utilization, seeking to establish a reasonable compromise between conflicting interests. Communities are beginning to consider baseflow conservation as the standard against which to measure groundwater sustainability. In the end, sustainability reflects resource conservation policy; the more conservative a policy, the more sustainable it is likely to be.

Impact of the proposed Campo landfill on the hydrology of the Tierra del Sol watershed. The impact that the proposed Campo landfill will have on the hydrology of the Tierra del Sol watershed is examined using an interdisciplinary perspective. Analysis of precipitation and well data suggests the presence of an effective hydraulic connection between surface water and groundwater in the region. Existing fracture maps and other geologic evidence reveal the extent to which the underlying aquifer is fractured. The presence of numerous springs and photogeologic lineaments indicates that water flows readily from the fractured-rock aquifer to the creeks, streams, and wells of the Tierra del Sol watershed. In fractured-rock aquifers, a leachate plume will move preferentially along the fractures. Advection is likely to be the predominant physical mechanism, with travel times from capture zone to nearby wells measured in days, rather than in years as would be the case in more traditional diffusion-dominated settings. Given the complexity of the fractured-rock system, the probability that leachate plumes will be missed by the system of monitoring wells is high. Thus, placing a major landfill on top of a fractured-rock aquifer such as Tierra del Sol's significantly compromises the health and welfare of the local population on both sides of the U.S.-Mexico border. Moreover, Tierra del Sol is part of the federally designated Campo-Cottonwood Sole Source Aquifer, i.e., it has been determined that, should this aquifer become contaminated, there are no reasonably available alternative sources of drinking water.

Groundwater utilization and sustainability. The indiscriminate and sometimes excessive use of groundwater has led to questions regarding its sustainability. To what extent can groundwater be exploited without unduly compromising the principle of sustainable development? The sustainability of groundwater utilization must be assessed from an interdisciplinary perspective, where hydrology, ecology, geomorphology, and climatology play an important role. Shallow groundwater flow systems should be distinguished from deep groundwater flow systems; the former interact with surface water, while the latter do not. Generally, groundwater does not recycle as fast as the surface water, with rates of groundwater turnover varying from years to millennia, depending on aquifer location, type, depth, properties, and connectivity. Excessive pumping can lead to groundwater depletion, where groundwater is extracted at a rate faster that it can be replenished. Unregulated groundwater use leads to the "Tragedy of the Commons," with the eventual depletion of the resource and ruin to all. The effects of excessive groundwater development tend to become apparent gradually, with time often measured in decades. To assure sustainability, studies must show that the hydrological, ecological, and other impacts of groundwater utilization are minimal. In addition to water quantity, sustainability must imply the preservation of water quality. for evapotranspiration.

Web-based engineering practice. The use of web-authoring tools such as HTML, CSS, PHP, MySQL, PERL and CGI to practice engineering teaching and research on the web. Examples are the following websites:

 ponce.sdsu.edu /  onlinechannel.sdsu.edu  onlinecomp.sdsu.edu  onlinehydro.sdsu.edu  onlineregression.sdsu.edu  onlinerouting.sdsu.edu  onlinetc.sdsu.edu  onlinewsprofiles.sdsu.edu  onlinewsprofiles2.sdsu.edu /  alamar.sdsu.edu  calculator.sdsu.edu  calculator2.sdsu.edu  calculator3.sdsu.edu  campcreek.sdsu.edu  carsandpeople.sdsu.edu  chezy.sdsu.edu  color.sdsu.edu  commons.sdsu.edu  ecolatrine.sdsu.edu  elnino.sdsu.edu  facets.sdsu.edu  globalwarming.sdsu.edu  groundwater.sdsu.edu  gwsustainability.sdsu.edu  historicalhydrology.sdsu.edu  manning.sdsu.edu  manningsn.sdsu.edu  manningsn2.sdsu.edu  milestones.sdsu.edu  mockus.sdsu.edu  perpetual.sdsu.edu  rational.sdsu.edu  saltonsea.sdsu.edu  severance.sdsu.edu  slopearea.sdsu.edu  tecate.sdsu.edu  threeissues.sdsu.edu  tierradelsol.sdsu.edu  tractiveforce.sdsu.edu  visualab.sdsu.edu

Dam-breach flood wave propagation using dimensionless parameters. The theory of linear stability is used to develop dimensionless parameters to propagate flood waves caused by dam breaches. At a certain dimensionless distance downstream, the flood stage is shown to be independent of a specially formulated Froude number based on breach peak discharge and outflow volume.