Presentations 2016

Evaluating the Effects of Over Pumping and Drought on Water Supply Well Production Capacities and Pumping Costs

University of California, Davis

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Significant decreases in groundwater elevations are generally caused by pumping more from groundwater basins than they can sustainably supply. Such over pumping can be especially pronounced during droughts when surface water supplies are low. The economic impacts caused by over pumping and drought include increased costs for supplying water and lost revenue from inability to meet water demand. In some cases, the combination of decreased groundwater elevation and existing well depth limits well production capacity as wells run dry. Also, decreased groundwater elevation limits well pump operating capacity and increases cost. Water supply wells are constructed to different depths depending upon a variety of factors that include production rate and water quality requirements, local hydrogeology, and projections of future conditions and supply needs. Deeper wells also have been constructed over time as conditions and construction methods have evolved. As a result, the depths of existing water supply wells vary over fairly wide ranges. Overall, shallower wells are more susceptible to impact from decreased groundwater elevations. Likewise, pumps are initially selected and installed in wells based upon specific existing conditions (i.e., desired production rate, standing groundwater elevation and hydraulic performance of the well) and operations are impacted by decreased groundwater elevations.As groundwater elevations decrease, costs may be incurred to move pumps deeper in the wells so the pumps are adequately submerged below pumping water levels. Further elevation decreases may increase production and maintenance costs, as well as decrease production capacity, as pumping levels drop into the screened intervals of wells and cause screen clogging. In more extreme cases, well replacement costs may be incurred as groundwater elevations drop so low that adequate submergence of pumps cannot be maintained and wells become unusable. Additionally, operating points on pump head-capacity curves shift towards lower production rates, efficiencies decrease and operating times to produce required volumes of water increase. All of these effects decrease production capacity and increase operating costs.The potential impacts of decreasing groundwater elevation on well pumping costs were evaluated for a study area located in California’s Central Valley (greater vicinity of Tulare, CA). Well constructions were characterized through statistical analysis of the elevations for the tops and bottoms of screened intervals obtained from well construction logs provided by the California Department of Water Resources (DWR). Groundwater elevation time series were obtained from the DWR Water Data Library. Estimated trends in well capacity loss were developed by determining the fraction of wells over time that had standing water levels (minus an estimated pumping drawdown) below 1) the top of the screened interval and 2) the bottom of the screened interval. Changes in pumping cost were evaluated by considering ranges in lift requirements based on the standing groundwater elevations (minus an estimated pumping drawdown) at different points in time. Trends in pumping costs were developed by calculating lift cost based on standard calculations. This presentation summarizes findings of groundwater well production capacities and pumping costs in the study area under sustained drought conditions.

Designing Production wells to Optimize Performance and Efficiency

Roscoe Moss Comapny

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There has never been a more critical time to design, operate, and maintain ground water production wells in the most cost efficient manner possible. This presentation will highlight the critical components of the well construction process; material selection, formation sampling, gravel pack selection, screen slot size selection, and well development. Proper application of these design and construction techniques can maximize the well’s production potential and service life. Additional topics will include the definition of well efficiency and a discussion on the hydraulic losses that contribute to drawdown in the well. The primary goal for designing and constructing an efficient well is to minimize the hydraulic losses which will reduce the drawdown in the well, thereby resulting in lower pumping costs for the well owner.

Groundwater, Bioenergy and Soil Health – Is the Nexus Sustainable?

USDA-Agricultural Research Service (ARS), National Laboratory for Agriculture and the Environment

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Human demand for food, feed, fiber, and fuel resources will continue to increase as our global population climbs steadily towards 9.5 billion or more. Our objective for this presentation is to review potential biofuel production impacts on U.S. groundwater availability and quality by examining interactions affecting the groundwater – bioenergy – soil health nexus. Currently, irrigation supports 40% of global food production, but it occupies only about 18% of the agricultural landscape. Groundwater resources, being used for critical, irrigated food production in several regions of the world, are being depleted because their recharge rates are well below extraction rates. Therefore, without significant improvements in irrigated water management, the life expectancy for many irrigation aquifers, including several in the United States, is projected to be decades or even less. Soil degradation is an equally important problem caused by many factors that can only be addressed by adopting sustainable agricultural and land management practices. Soil and water resources are intimately linked. Addressing the nexus is the only way to ensure solutions for one problem do not induce unintended consequences for the other. Furthermore, to ensure consensus, acceptance, and implementation, it will be essential to embrace multi-Agency/institution, non-government organization (NGO), and private-sector inputs and perspectives using integrated systems approaches. The water analysis tool for energy resources (WATER) developed by Department of Energy (DOE) engineers, land use and cropping systems changes as well as enhanced irrigation water management strategies being developed by ARS scientists and engineers, and policy changes being recommended by several university Water Resource Institutes will be discussed. Our hypothesis is that all of these tools and many more will be needed to address this wicked problem, and thus ensure our fragile, groundwater, energy, and soil health requirements are met within a truly sustainable nexus.

RZWQM simulations of nitrate loss to subsurface drains from a Midwest bioenergy production system

USDA-ARS

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Goals have been established to replace 30% of U.S. transportation fuels that are currently derived from petroleum with biofuels by 2030. The allowable quantity of first-generation, corn (Zea mays L.) grain-based biofuel (i.e., ethanol) has been capped at 15 billion gallons, thus requiring 16 billion gallons of second generation, biofuels to be derived from various cellulosic feedstock sources. Due to global demand for corn grain, not only for biofuel but also as an animal feed, food, and export commodity, the crop has been planted in the U.S. on an average of 88.9 million acres each year between 2005 and 2015. From a sustainability perspective, increased corn production has had positive economic benefits, but environmentally, corn production is a “leaky” process that has resulted in substantial loss of nitrate to surface and groundwater resources and thus created tensions between rural and urban sectors of our society. Incorporating a cover crop such as cereal rye (Triticale cereale L.) into current cropping systems, water quality concerns can be mitigated and demands for corn grain, stover, and other cellulosic feedstock can be met. The Root Zone Water Quality Model (RZWQM) was used to estimate the effects of corn production with and without a winter rye cover crop on shallow groundwater quality. We used a calibrated and tested version of RZWQM to estimate N loss in subsurface drainage (1.2 m) assuming a sustainable amount of corn stover (~1.7 tons/acre or 50% of the residue from a 175 bu/acre crop) is harvested and a winter cover crop is grown. Simulated nitate-N dynamics with or without harvesting the cover crop will help determine if both economic and environmental sustainability goals can be met.

N-E-W Tech™: Advancing the Agricultural Circular Economy at the Nutrient-Energy-Water Nexus with Technology Innovation

University of Idaho

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Water sustainability is the most critical challenge to the future of agriculture. Concomitant with the challenges of a changing climate, new ground and surface water quality directives, and increasing water competition and food demand from a growing population, agriculture will certainly need to adapt to change in the waterscape of the future. N-E-W Tech™ is an innovative water treatment process at the nutrient, energy, and water nexus. N-E-W Tech™ integrates reactive filtration with iron-functionalized biochar and ozone for catalytic oxidation water treatment, sterilizing reclaimed water, and producing a value-added nutrient upcycled, Enhanced Efficiency Fertilizer (EEF) product that addresses the need for carbon sequestration, rhizosphere nutrient and moisture stability and soil tilth. Our membrane-free approach addresses the negative aspects of several current alternative technologies to water reuse and recycling including their high energy inputs, removal but not destruction of contaminants and pathogens, high capital-maintenance-operations costs, and their poorer sustainability footprint. In this work we report on the design-build, water treatment performance, energy efficiency and general operations of this technology built as a 15 gpm pilot process on a mobile trailer. Recognized as one of twenty-five innovations that changed the world, reactive filtration is our commercialized, high efficiency nutrient removal process installed at 10+ MGD at water treatment plants; it uses an iron oxyhydroxide adsorptive process in a moving sand bed filter. In N-E-W Tech™ we demonstrate the addition and recovery of 1 to 10 grams of micronized iron-functionalized biochar per gallon, using this substrate as a sorbent and as a sacrificial catalyst with ozone to form hydroxyl radicals. Oxidizing potentials ranging from 1100 to 1300+ mV are maintained in the reactor during the 10-15 minute process time. Nutrients selectively adsorb to the recovered functionalized biochar demonstrating fertilizer potential in this carbon sequestering substrate. Initial N-E-W Tech™ effluent results from municipal secondary water demonstrate turbidity <0.5 NTU, 3+ log removal of microbial pathogens, total P <10 ppb and other promising results that indicate a positive future for the use of degraded water resources for the agricultural circular economy.