Sustainability and groundwater

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

Floods in changing streams

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

Sustainable groundwater management: The theory of a game

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

New standards for probabilistic fitting of saturated hydraulic conductivity

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

Assessment of seawater intrusion potential from sea level rise in coastal aquifers of California

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

The Flooding and Drying Cycles in Rain-fed Seasonal Meadows, Central California

Wetlands are areas with hydric (poorly drained) soils or rocky substrate covered permanently or intermittently by shallow water that support predominantly hydrophytes. In a natural setting, they are created by the convergence of topographic, hydraulic, climatic, and hydrogeologic conditions favorable to maintaining saturated soils or ponding for extended periods. Wetlands serve important water-quality and ecological functions. In this paper we present a method to quantify the water balance and flooding duration in rain-fed wetlands with negligible overland drainage and a deep groundwater table. The method imposes Horton or Green-and-Ampt infiltration on design storms to determine the mechanics of wetland ponding and drying. The Green-and-Ampt infiltration analysis is based on a solution technique that considers variable rainfall supply, evapotranspiration, and ponding. The water balance method is useful in wetland creation and restoration, and particularly well suited to calculate the flooding-drying cycle of vernal pools endemic to California and southern Oregon. The method is also applicable to the analysis of ponding in irrigated, flat, terrain. Copyright ASCE 2005

Environmental impacts of groundwater overdraft: selected case studies in the southwestern United States

The southwestern United States - this paper's study region - is home to large urban centers and features a thriving agro-industrial economic sector. This region is also one of the driest in North America, with highly variable seasonal and inter-annual precipitation regimes and frequent droughts. The combination of a large demand for usable water and semi-arid climate has led to groundwater overdraft in many important aquifers of the region. Groundwater overdraft develops when long-term groundwater extraction exceeds aquifer recharge, producing declining trends in aquifer storage and hydraulic head. In conjunction with overdraft, declines in surface-water levels and streamflow, reduction or elimination of vegetation, land subsidence, and seawater intrusion are well documented in many aquifers of the southwestern United States. This work reviews case studies of groundwater overdraft in this region, focusing on its causes, consequences, and remedial methods applied to counter it

Climate-change impacts in a regional karst aquifer, Texas, USA

Climate-change scenarios were created from scaling factors derived from several general circulation models to assess the likely impacts of aquifer pumping on the water resources of the Edwards Balcones Fault Zone (BFZ) aquifer, Texas, one of the largest aquifer systems in the United States. Historical climatic time series in periods of extreme water shortage (1947-1959), near-average recharge (1978-1989), and above-average recharge (1975-1990) were scaled to 2 x CO2 conditions to create aquifer recharge scenarios in a warmer climate. Several pumping Scenarios were combined with 2 x CO2 climate scenarios to assess the sensitivity of water resources impacts to human-induced stresses on the Edwards BFZ aquifer. The 2 X CO2 climate-change scenarios were linked to surface hydrology and used to drive aquifer dynamics with alternative numerical simulation models calibrated to the Edwards BFZ aquifer. Aquifer simulations indicate that, given the predicted growth and water demand in the Edwards BFZ aquifer region, the aquifer's ground water resources appear threatened under 2 x CO2 climate scenarios. Our simulations indicate that 2 X CO2 climatic conditions could exacerbate negative impacts and water shortages in the Edwards BFZ aquifer even if pumping does not increase above its present average level. The historical evidence and the results of this article indicate that without proper consideration to variations in aquifer recharge and sound pumping strategies, the water resources of the Edwards BFZ aquifer could be severely impacted under a warmer climate. (C) 2000 Elsevier Science B.V

Spatial and Temporal Downscaling of TRMM Precipitation with Novel Algorithms Spatial and Temporal Downscaling of TRMM Precipitation with Novel Algorithms

Abstract: Tropical Rainfall Measuring Mission (TRMM) satellite products constitute valuable precipitation datasets over regions with sparse rain gauge networks. Downscaling is an effective approach to estimating the precipitation over ungauged areas with high spatial resolution. However, a large bias and low resolution of original TRMM satellite images constitute constraints for practical hydrologic applications of TRMM precipitation products. This study contributes two precipitation downscaling algorithms by exploring the nonstationarity relations between precipitation and various environment factors [daytime surface temperature (LTD), terrain slope, normalized difference vegetation index (NDVI), altitude, longitude, and latitude] to overcome bias and low-resolution constraints of TRMM precipitation. Downscaling of precipitation is achieved with the geographically weighted regression model (GWR) and the backward-propagation artificial neural networks (BP_ANN). The probability density function (PDF) algorithm corrects the bias of satellite precipitation data with respect to spatial and temporal scales prior to downscaling. The principal component analysis algorithm (PCA) provides an alternative method of obtaining accurate monthly rainfall estimates during the wet rainfall season that minimizes the temporal uncertainties and upscaling effects introduced by direct accumulation (DA) of precipitation. The performances of the proposed downscaling algorithms are assessed by downscaling the latest version of TRMM3B42 V7 datasets within Hubei Province from 0.25° (about 25 km) to 1-km spatial resolution at the monthly scale. The downscaled datasets are systematically evaluated with in situ observations at 27 rain gauges from the years 2005 through 2010. This paper’s results demonstrate the bias correction is necessary before downscaling. The high-resolution precipitation datasets obtained with the proposed downscaling model with GWR relying on the NDVI and slope are shown to improve the accuracy of precipitation estimates. GWR exhibits more accurate downscaling results than BP_ANN coupled with the genetic algorithm (GA) in most dry and wet seasons