A theory of sustainable groundwater exploitation is presented in this article. The core of the article is a general formulation of the mathematical programming problem whose solution-when it exists-produces sustainable pumping rates. A simplified quadratic, linearly constrained, version of the general formulation is implemented and solved to calculate sustainable pumping rates in terms of diverse economic and hydraulic factors. The calculated pumping rates confirm the desirability of sustainable groundwater strategies judged by aquifer and economic performance.

Flood damage continues to rise in many parts of the world, even when measured in constant monetary units. The rise in flood damage is caused in some instances by the human settlement of flood plains, which augments the stock of property and exposed population within flood-prone areas. In other instances, flood damage increases in response to the cumulative effects of watershed impacts on the streamflow response to precipitation. In addition, the large uncertainty which surrounds the estimates of rare flood events, especially in ungauged streams, frequently leads to the under-estimation of flood risk. This article examines key factors that effect time-changing flood damage, and presents a case study that illustrates human-induced contributions to flood damage.

Principles of sustainable groundwater exploitation are presented in this article. The renewable and inappropriable nature of groundwater is examined in light of the process of recharge. An example illustrates the interplay among groundwater extraction, recharge, natural recharge, and storage. It demonstrates the aquifer-specific characteristics of overdraft and replenishment, which are driven by climatic variability and the rate of groundwater mining. A second example uses game theoretic methodology to quantify the roles of cooperation and non-cooperation on groundwater extraction. The economic and environmental advantages of cooperative groundwater extraction are demonstrated with data from a coastal aquifer.

The KSTAT Standard Committee of the Environmental Water Resources Institute (EWRI) and the American Society of Civil Engineers (ASCE) initiated activities in year 2005. Over the last two years, the KSTAT Committee has produced two preliminary standard-guidance documents expected to be published by ASCE following public review. This paper summarizes the key methods presented in the two standard-guidance documents, highlighting the potential areas of application in groundwater hydrology and geotechnical engineering. © 2007 ASCE.

The design of groundwater monitoring networks is a function of 1) the statistical heterogeneity and geologicl anisotropy of the aquifer; 2) the hydrodynamics of plume migration; 3) the practical decisions that result from a data acquisition program; 4) budgetary constraints imposed on available resources. The joint treatment of such factors and their incorporation on a mathematical (combinatorial) formulation of the problem to determine the best well locations was given in this paper. The next step should be the application to an actual design. Efforts are in progress in this direction; the mathematical conceptualization and commanding factors in groundwater network design has been set in this work. -from Author

It is shown that runs of low-flow annual streamflow in a coastal semiarid basin of Central California can be adequately modelled by renewal theory. For example, runs of below-median annual streamflows are shown to follow a geometric distribution. The elapsed time between runs of below-median streamflow are geometrically distributed also. The sum of these two independently distributed geometric time variables defines the renewal time elapsing between the initiation of a low-flow run and the next one. The probability distribution of the renewal time is then derived from first principles, ultimately leading to the distribution of the number of low-flow runs in a specified time period, the expected number of low-flow runs, the risk of drought, and other important probabilistic indicators of low-flow. The authors argue that if one identifies drought threat with the occurrence of multiyear low-flow runs, as it is done by water supply managers in the study area, then our renewal model provides a number of interesting results concerning drought threat in areas historically subject to inclement, dry, climate. A 430-year long annual streamflow time series reconstructed by tree-ring analysis serves as the basis for testing our renewal model of low-flow sequences. © Springer-Verlag 1996.

The importance of the Gumbel probability distribution for the description of extreme hydrologic events is examined in this article. The key findings of this work are: (1) an iterative method of least squares was developed and found to be well-suited for the efficient fitting of the two-parameter Gumbel distribution to hydrologic extremes; (2) negative truncation is necessary to adequately describe hydrologic minima (non-negative) data, while the standard Gumbel distribution for maxima is well-suited for modeling extreme (large) hydrologic events; (3) the distribution function of the sum of two independent Gumbel variables, of importance in hydrology, has been derived and successfully applied to spring flow data. Several examples that involve the modeling of hydrologic extremes are presented and analyzed.

The aim of this project is to develop a model of saltwater intrusion potential due to sea level rise for the next one hundred years on two groundwater basins in California - Seaside and Oxnard. FEFLOW finite element modeling software is used to render the three-dimensional hydrogeologic structure of each aquifer and to model the flow of groundwater and change in salt concentration over time.

A study was conducted to evaluate the effects of dynamic movement of groundwater on the management of operation near Aquifer Storage and Recovery (ASR) operations using geochemical tracers and numerical modeling at the Kern Water Bank (KWB) San Joaquin Valley, Kern County, California. Groundwater samples were collected from a shallow and a deep monitoring well and analyzed for Chlorofluorocarbons (CFC-11 and CFC-12), and stable isotopes of the water. The CFC data shows that young water is found in the northern and central regions of the KWB at shallow depths. An intermediate aged groundwater component is found in the deeper wells of the northern and central regions and the oldest water is found in the southern and western areas. The CDWR numerical flow model was used in the study and was optimized for an earlier time period, under different recharge and pumping rates.

Leading methods for the evaluation of submarine groundwater discharge are presented, and their possible application under different hydrogeological conditions is discussed.