Federal Decentralization and Adaptive Management of Water Resources: Reservoir Reallocation by the U.S. Army Corps of Engineers

Reservoir operations must respond to changing conditions, such as climate, water demand, regulations, and sedimentation. The U.S. Army Corps of Engineers (Corps) can reallocate reservoir storage to respond to such changes. We assembled and analyzed a database of reservoir reallocations implemented and proposed by the Corps. While only a small portion of total reservoir storage nationwide has been reallocated, there are substantial differences in reallocation frequency and magnitude across the nation: some Corps Districts and Divisions use reallocation while others do not, relying more on discretion and small‐scale adaptation of operations. This difference illustrates how water resource agencies like the Corps decentralize management decisions to allow responding to disparate conditions. Decentralized decision‐making provides a responsive approach to water management, while centralized and hierarchical decision‐making is a slower, more deliberative approach. Decentralized decision‐making may lead to the accumulation of short‐term, local decisions over time to the point that the system is managed differently than anticipated. Reallocation, which is a form of planned adaptive management, can be accommodating of multiple competing demands and different stakeholders, yet expensive and less temporally responsive. The challenge for any large water resource management agency is to balance between local‐level, responsive discretion vs. centralized, planned decision‐making.     

QUALITY STUDY OF GRAYWATER TREATMENT SYSTEMS1

ABSTRACT: A residential single family dwelling was retrofitted to recycle graywater for landscape irrigation and toilet flushing. The objective of this study was to determine improvements in graywater quality by evaluating five simple graywater treatment systems that were easily adapted to the household plumbing. The treatment systems consisted of (1) water hyacinths and sand filtration, (2) water hyacinths, copper ion disinfection, and sand filtration, (3) copper ion disinfection and sand filtration, (4) copper/silver ion disinfection and sand filtration, and (5) 20–μm cartridge filtration. Water quality parameters measured were fecal and total coliform indicator bacteria, nitrates, suspended solids, and turbidity. Reductions in bacterial concentration, suspended solids and turbidity were achieved by all systems tested. Treatment reduced nitrate concentrations to an average of 2.6 mg/liter. Reductions in suspended solids, and turbidity were influenced more by the quality of the graywater entering the treatment system than the efficiency of the systems themselves. The water hyacinths and sand filtration system provided the best graywater quality in terms of the concentrations of fecal indicator bacteria. The system providing the best water quality in regard to average suspended solids after treatment was the water hyacinths, copper ion, and sand filtration system, and the best average turbidity was achieved by the copper/silver ion generating unit with sand filtration. All systems were capable of significant reductions in fecal indicator bacteria, suspended solids, and turbidity; however, additional treatment or disinfection would be necessary to further reduce the level of coliform and fecal coliform bacteria to achieve regulatory standards in the State of Arizona.     

TMDL Balance: A Model for Coastal Water Pollutant Loadings

Bacterial contamination accounts for more than 60% of the impairments included on the 2008 Texas 303(d) List. Many of these bacterial impairments are along the Texas Gulf Coast because coastal waters often are regulated for oyster harvesting, which have strict water quality standards. Under the Clean Water Act, each one of these impaired waterbodies requires a total maximum daily load (TMDL) study to be performed. A recent, statewide study recommended the development and application of simple modeling approaches to address the majority of Texas's bacteria TMDLs, including “… simple load duration curve, GIS [geographic information systems], and/or mass balance models.” We developed the TMDL Balance model in response to this recommendation. TMDL Balance is a steady state, mass balance, GIS‐based model for simulating pollutant loads and concentrations in coastal systems. The model uses plug‐flow reactor and continuously‐stirred tank reactor equations to route spatially distributed point and nonpoint source loads through a watershed via overland flow, non‐tidal flow, and tidal flow, decaying the loads via first‐order kinetics. In this paper, we explain the development of the watershed loading portion of the TMDL Balance model, demonstrating the methodology through a case study: computing bacterial loads in the Copano Bay watershed of southeast Texas. The application highlights an example of distributing bacterial sources spatially based on land use data.     

DROUGHT,TREE RINGS,AND RESERVOIR DESIGN1

Droughts constitute one of the most important factors affecting the design and operation of water resources infrastructure. Hydrologists ascertain their duration, severity, and pattern of recurrence from instrumental records of precipitation or stream‐flow. Under suitable conditions, and with proper analysis, tree rings obtained from long living, climate sensitive species of trees can extend instrumental records of streamflow and precipitation over periods spanning several centuries. Those tree‐ring “reconstructions” provide a valuable insight about climate variability and drought occurrence in the Holocene, and yield long term hydrological data useful in the design of water infrastructure. This work presents a derivation of drought risk based on a renewal model of drought recurrence, a brief review of the basic theory of tree‐ring reconstructions, and a stochastic model for optimizing the design of water supply reservoirs. Examples illustrate the methodology developed in this work and the supporting role that tree‐ring reconstructed streamflow can play in characterizing hydrologic variability.     

USING REFERENCE SITES AND SIMPLE LINEAR REGRESSION TO ESTIMATE LONG‐TERM WATER LEVELS IN COASTAL PLAIN FORESTS1

ABSTRACT: The ability of regulators, resource managers, and consultants to assess accurately wetland hydrology is crucial when identifying and delineating wetlands. In this study, simple linear regression and long‐term (ten year) New Jersey Pinelands stream gaging and pitch pine lowland water‐level data sets were used to estimate long‐term hydroperiods at lowland test sites with short‐term (two year) records. Separate regression equations were developed for each test site using reference site data and stream gaging data, and two sets of equations for selected test sites were produced using two different short‐term periods of record. Test sites had long‐term records ranging from four to ten years, allowing validation of the regression models. Measured and predicted test site growing season water levels were similar regardless of which short‐term period of record was used. The results based on the stream gaging site data were similar, although the difference between measured and estimated growing season water levels was greater when this approach was used. Excellent agreement was found between measured and estimated frequencies of near‐surface saturation at test sites for each growing season month, and these relationships improved when cumulative, seasonal frequencies were considered. The reference wetland approach used in this study may have its greatest value in regions with both high development pressures and problem wetlands and may provide an effective way of resolving costly wetland delineation disputes.     

BIODEGRADATION OF DISINFECTION BYPRODUCTS AS A POTENTIAL REMOVAL PROCESS DURING AQUIFER STORAGE RECOVERY1

ABSTRACT: The biodegradation potential of two drinking water disinfection byproducts was investigated using aquifer materials obtained from approximately 100 and 200 meters below land surface in an aerobic aquifer system undergoing aquifer storage recovery of treated surface water. No significant biodegradation of a model trihalomethane compound, chloroform, was observed in aquifer microcosms under aerobic or anaerobic conditions. In contrast, between 16 and 27 percent mineralization of a radiolabeled model haloacetic acid compound, chloroacetic acid, was observed. These results indicate that although the potential for biodegradation of chloroacetic acid exists in deep aquifer systems, chloroform entrained within these aquifers or formed in situ will tend to persist. These results have important implications for water managers planning to meet anticipated lowered permissible levels of trihalomethanes in drinking water.     

Assessment of Residential Rain Barrel Water Quality and Use in Cincinnati,Ohio1

The collection, storage, and reuse of rainwater collected in rain barrels from urban rooftop areas assists municipalities in achieving stormwater management objectives and in some areas also serves as an adjunct resource for domestic water supplies. In this study, rainwater reuse and levels of select microbial indicators were monitored for six residential rain barrels located in the Shepherd Creek watershed of Cincinnati, Ohio. Water from rain barrels typically had poor microbial quality and was used for watering indoor and outdoor plants. Rain barrel water chemistry was slightly acidic, exhibited wide ranges in conductivity, turbidity, and total organic carbon (TOC) concentrations and gave no evidence of the presence of cyanobacterial microcystin toxins. Selected microbial water‐quality indicators indicated that counts of total coliform and enterococci were consistently above U.S. Environmental Protection Agency standards for secondary recreational contact water‐quality standards. Residential rain barrels can provide water appropriate for low‐contact reuses (such as plant watering), although there may be transient periods of high levels of indicator bacteria in the collected water.     

FISH AND WILDLIFE ENHANCEMENT THROUGH WATER RESOURCES DEVELOPMENT1

.Fish and wildlife enhancement through water resources development implies fish and wildlife will be enhanced or benefit directly from such development. As a matter of practicality, the opposite may be the case in that wildlife lands of prime value and stream fisheries are often lost or severely altered as a result of reservoir construction or stream channelization. Additionally, estuarine fish and wildlife can also suffer from water resources development due to reductions in volume of fresh waters reaching the estuaries and adjacent marshes. In some instances waterfowl habitat can be created by reservoir construction and with good planning waterfowl habitat and use may be enhanced. To offset losses of thousands of acres of wildlife habitat when a river system is to be totally harnessed, planners could set aside sufficiently large natural areas dedicated for use by wildlife. This, however, would be replacement rather than enhancement. Reservoir fisheries can be enhanced with good planning to include timber clearing, shoreline clearing, boat road clearing, variable level drawoff devices and tailrace escapement channels. To sum up, it is possible for some species offish and wildlife to be enhanced through water resources development but only at the expense of others, and then only through careful and integrated planning.     

HERBICIDES AND TRANSFORMATION PRODUCTS IN SURFACE WATERS OF THE MIDWESTERN UNITED STATES1

ABSTRACT: Most herbicides applied to crops are adsorbed by plants or transformed (degraded) in the soil, but small fractions are lost from fields and either move to streams in overland runoff, near surface flow, or subsurface drains, or they infiltrate slowly to ground water. Herbicide transformation products (TPs) can be more or less mobile and more or less toxic in the environment than their source herbicides. To obtain information on the concentrations of selected herbicides and TPs in surface waters of the Midwestern United States, 151 water samples were collected from 71 streams and five reservoir outflows in 1998. These samples were analyzed for 13 herbicides and 10 herbicide TPs. Herbicide TPs were found to occur as frequently or more frequently than source herbicides and at concentrations that were often larger than their source herbicides. Most samples contained a mixture of more than 10 different herbicides or TPs. The ratios of TPs to herbicide concentrations can be used to determine the source of herbicides in streams. Results of a two‐component mixing model suggest that on average 90 percent or more of the herbicide mass in Midwestern streams during early summer runoff events originates from the runoff and 10 percent or less comes from increased ground water discharge.     

Models,Assumptions, and Stakeholders: Planning for Water Supply Variability in the Colorado River Basin1

Abstract: Declining reservoir storage has raised the specter of the first water shortage on the Lower Colorado River since the completion of Glen Canyon and Hoover Dams. This focusing event spurred modeling efforts to frame alternatives for managing the reservoir system during prolonged droughts. This paper addresses the management challenges that arise when using modeling tools to manage water scarcity under variable hydroclimatology, shifting use patterns, and institutional complexity. Assumptions specified in modeling simulations are an integral feature of public processes. The policymaking and management implications of assumptions are examined by analyzing four interacting sources of physical and institutional uncertainty: inflow (runoff), depletion (water use), operating rules, and initial reservoir conditions. A review of planning documents and model reports generated during two recent processes to plan for surplus and shortage in the Colorado River demonstrates that modeling tools become useful to stakeholders by clarifying the impacts of modeling assumptions at several temporal and spatial scales. A high reservoir storage‐to‐runoff ratio elevates the importance of assumptions regarding initial reservoir conditions over the three‐year outlook used to assess the likelihood of reaching surplus and shortage triggers. An ensemble of initial condition predictions can provide more robust initial conditions estimates. This paper concludes that water managers require model outputs that encompass a full range of future potential outcomes, including best and worst cases. Further research into methods of representing and communicating about hydrologic and institutional uncertainty in model outputs will help water managers and other stakeholders to assess tradeoffs when planning for water supply variability.     

消毒技术去除饮用水中病原微生物的研究进展

饮用水中存在着不同种类的病原微生物,这些病原微生物给人体健康带来危害。本文简要介绍常规消毒技术去除饮用水中病原微生物的研究现状;常规消毒剂仍然是现代饮用水处理工艺使用的主要消毒剂;近些年来,对常规消毒剂联合消毒的协同作用和联合消毒剂的概念提出了探讨,认为联合消毒荆是今后饮用水去除病原微生物的发展趋势;膜技术这种物理消毒技术,由于其高效性而得到广泛关注,膜消毒去除病原微生物也成为当今消毒技术研究的热点。     

RIVERWARE: A GENERALIZED TOOL FOR COMPLEX RESERVOIR SYSTEM MODELING1

ABSTRACT: Water management agencies seek the next generation of modeling tools for planning and operating river basins. Previous site‐specific models such as U.S. Bureau of Reclamation's (USBR) Colorado River Simulation System and Tennessee Valley Authority's (TVA) Daily Scheduling Model have become obsolete; however, new models are difficult and expensive to develop and maintain. Previous generalized river basin modeling tools are limited in their ability to represent diverse physical system and operating policy details for a wide range of applications. RiverWare(tm), a new generalized river basin modeling tool, provides a construction kit for developing and running detailed, site‐specific models without the need to develop or maintain the supporting software within the water management agency. It includes an extensible library of modeling algorithms, several solvers, and a rich “language” for the expression of operating policy. Its point‐and‐click graphical interface facilitates model construction and execution, and communication of policies, assumptions and results to others. Applications developed and used by the TVA and the USBR demonstrate that a wide range of operational and planning problems on widely varying basins can be solved using this tool.     

EVAPOTRANSPIRATION AND SOIL MOISTURE DYNAMICS ON A SEMIARID PONDEROSA PINE HILLSLOPE1

ABSTRACT: Detailed measurements of soil moisture and ET in semiarid forest environments have not been widely reported in the literature. In this study, soil moisture and water balance components were measured over a four‐year period on a semiarid ponderosa pine hillslope, with evapotranspiration (ET) determined as the residual of measured precipitation, runoff, and change in soil moisture storage. ET accounts for approximately 95 percent of the water budget and has a distinctly bimodal annual pattern, with peaks occurring after spring snowmelt and during the late summer monsoon season, periods that coincide with high soil moisture. Weekly growing season ET rates determined by the hillslope water balance are found to be invariably below calculated potential rates. Normalized ET rates are linearly correlated (r²= 0.62) with soil moisture; therefore, a simple linear relation is proposed. Growing season soil moisture dynamics were modeled based on this relation. Results are in fair agreement (r²= 0.63) with the observed soil moisture data over the four growing seasons; however, for two dry summers with little surface runoff, much better results (r² > 0.90) were obtained.     

A Streamflow Forecasting Framework using Multiple Climate and Hydrological Models1

Abstract: Water resources planning and management efficacy is subject to capturing inherent uncertainties stemming from climatic and hydrological inputs and models. Streamflow forecasts, critical in reservoir operation and water allocation decision making, fundamentally contain uncertainties arising from assumed initial conditions, model structure, and modeled processes. Accounting for these propagating uncertainties remains a formidable challenge. Recent enhancements in climate forecasting skill and hydrological modeling serve as an impetus for further pursuing models and model combinations capable of delivering improved streamflow forecasts. However, little consideration has been given to methodologies that include coupling both multiple climate and multiple hydrological models, increasing the pool of streamflow forecast ensemble members and accounting for cumulative sources of uncertainty. The framework presented here proposes integration and offline coupling of global climate models (GCMs), multiple regional climate models, and numerous water balance models to improve streamflow forecasting through generation of ensemble forecasts. For demonstration purposes, the framework is imposed on the Jaguaribe basin in northeastern Brazil for a hindcast of 1974‐1996 monthly streamflow. The ECHAM 4.5 and the NCEP/MRF9 GCMs and regional models, including dynamical and statistical models, are integrated with the ABCD and Soil Moisture Accounting Procedure water balance models. Precipitation hindcasts from the GCMs are downscaled via the regional models and fed into the water balance models, producing streamflow hindcasts. Multi‐model ensemble combination techniques include pooling, linear regression weighting, and a kernel density estimator to evaluate streamflow hindcasts; the latter technique exhibits superior skill compared with any single coupled model ensemble hindcast.     

BASIN SCALE WATER MANAGEMENT AND FORECASTING USING ARTIFICIAL NEURAL NETWORKS1

ABSTRACT: Water scarcity in the Sevier River Basin in south‐central Utah has led water managers to seek advanced techniques for identifying optimal forecasting and management measures. To more efficiently use the limited quantity of water in the basin, better methods for control and forecasting are imperative. Basin scale management requires advanced forecasts of the availability of water. Information about long term water availability is important for decision making in terms of how much land to plant and what crops to grow; advanced daily predictions of streamflows and hydraulic characteristics of irrigation canals are of importance for managing water delivery and reservoir releases; and hourly forecasts of flows in tributary streams to account for diurnal fluctuations are vital to more precisely meet the day‐to‐day expectations of downstream farmers. A priori streamflow information and exogenous climate data have been used to predict future streamflows and required reservoir releases at different timescales. Data on snow water equivalent, sea surface temperatures, temperature, total solar radiation, and precipitation are fused by applying artificial neural networks to enhance long term and real time basin scale water management information. This approach has not previously been used in water resources management at the basin‐scale and could be valuable to water users in semi‐arid areas to more efficiently utilize and manage scarce water resources.     

POTENTIAL EFFECTS OF CLIMATE CHANGE ON SURFACE‐WATER QUALITY IN NORTH AMERICA1

ABSTRACT: Data from long‐term ecosystem monitoring and research stations in North America and results of simulations made with interpretive models indicate that changes in climate (precipitation and temperature) can have a significant effect on the quality of surface waters. Changes in water quality during storms, snowmelt, and periods of elevated air temperature or drought can cause conditions that exceed thresholds of ecosystem tolerance and, thus, lead to water‐quality degradation. If warming and changes in available moisture occur, water‐quality changes will likely first occur during episodes of climate‐induced stress, and in ecosystems where the factors controlling water quality are sensitive to climate variability. Continued climate stress would increase the frequency with which ecosystem thresholds are exceeded and thus lead to chronic water‐quality changes. Management strategies in a warmer climate will therefore be needed that are based on local ecological thresholds rather than annual median condition. Changes in land use alter biological, physical, and chemical processes in watersheds and thus significantly alter the quality of adjacent surface waters; these direct human‐caused changes complicate the interpretation of water‐quality changes resulting from changes in climate, and can be both mitigated and exacerbated by climate change. A rigorous strategy for integrated, long‐term monitoring of the ecological and human factors that control water quality is necessary to differentiate between actual and perceived climate effects, and to track the effectiveness of our environmental policies.     

IMPLICATIONS OF ON‐GROUND NITROGEN LOADING AND SOIL TRANSFORMATIONS ON GROUND WATER QUALITY MANAGEMENT1

ABSTRACT: This paper presents a modeling approach based on a geographic information system (GIS) to estimate the variability of on‐ground nitrogen loading and the corresponding nitrate leaching to ground water. The methodology integrates all point and nonpoint sources of nitrogen, the national land cover database, soil nitrogen transformations, and the uncertainty of key soil and land use‐related parameters to predict the nitrate mass leaching to ground water. The analysis considered 21 different land use classes with information derived from nitrogen sources such as fertilizer and dairy manure applications, dairy lagoons, septic systems, and dry and wet depositions. Simulations were performed at a temporal resolution of one month to capture seasonal trends. The model was applied to a large aquifer of 376 square miles in Washington State that serves more than 100,000 residents with drinking water. The results showed that dairy manure is the main source of nitrogen in the area followed by fertilizers. It was also seen that nitrate leaching is controlled by the recharge rate, and there can be a substantial buildup of soil nitrogen over long periods of time. Uncertainty analysis showed that denitrification rate is the most influential parameter on nitrate leaching. The results showed that combining management alternatives is a successful strategy, especially with the use of nitrification inhibitors. Also, change in the land use pattern has a noticeable impact on nitrate leaching.     

饮用水消毒副产物控制工艺研究进展

通过对氯、二氧化氯、紫外线等常见消毒工艺以及去除已生成消毒副产物的深度处理工艺进行了分析,探讨了各种消毒工艺的消毒性能和对消毒副产物的控制效果以及各种深度处理工艺对消毒副产物的去除性能,为实际水处理中消毒以及深度处理工艺的选择提供了参考。     

Loss Rates from Lake Powell and Their Impact on Management of the Colorado River

As demand for water in the southwestern United States increases and climate change potentially decreases the natural flows in the Colorado River system, there will be increased need to optimize the water supply. Lake Powell is a large reservoir with potentially high loss rates to bank storage and evaporation. Bank storage is estimated as a residual in the reservoir water balance. Estimates of local inflow contribute uncertainty to estimates of bank storage. Regression analyses of local inflow with gaged tributaries have improved the estimate of local inflow. Using a stochastic estimate of local inflow based on the standard error of the regression estimator and of gross evaporation based on observed variability at Lake Mead, a reservoir water balance was used to estimate that more than 14.8 billion cubic meters (Gm³) has been stored in the banks, with a 90% probability that the value is actually between 11.8 and 18.5 Gm³. Groundwater models developed by others, observed groundwater levels, and simple transmissivity calculations confirm these bank storage estimates. Assuming a constant bank storage fraction for simulations of the future may cause managers to underestimate the actual losses from the reservoir. Updated management regimes which account more accurately for bank storage and evaporation could save water that will otherwise be lost to the banks or evaporation.     

Occurrence of Primidone,Carbamazepine, Caffeine,and Precursors for N‐Nitrosodimethylamine in Drinking Water Sources Impacted by Wastewater1

Abstract: Wastewater impact on drinking water sources was assessed using several approaches, including analysis of three pharmaceuticals and personal care products (PPCPs) – primidone, carbamazepine, and caffeine – as indicators, and determination of precursor concentrations for the disinfection byproduct N‐nitrosodimethylamine (NDMA) using formation potential (FP) tests. Samples were collected in 2006 and 2007 in rivers impacted by wastewater treatment plant (WWTP) discharges, at drinking water treatment plant (DWTP) intakes upstream or downstream from these discharges, and from two WWTP effluents in two watersheds. The levels [10th percentile ? maximum (median)] of primidone, carbamazepine, caffeine, and NDMAFP were 2‐95 (7) ng/l, 2‐207 (18) ng/l, 7‐687 (78) ng/l, and 12‐321 (35) ng/l, respectively. The highest concentrations of primidone, carbamazepine, and NDMA precursors were from one of the WWTP effluents, whereas the highest concentration of caffeine was detected in a river heavily impacted by treated wastewater discharges. The lowest concentrations of the three PPCPs were from a DWTP influent upstream of a metropolitan urban area with minimum wastewater impact. Temporal variations in PPCP and NDMAFP concentrations and streamflows in two selected watersheds were also observed. Furthermore, correlation analysis between caffeine or carbamazepine and primidone was evaluated. The results show that measurement of the two pharmaceuticals and NDMAFP tests can be used to evaluate wastewater impact in different watersheds, whereas caffeine results were more variable.