Michael E. Barber

SWAT modeling with uncertainty and cluster analyses of tillage impacts on hydrological processes

The impacts of tillage practices, majorly conventional tillage (CT) and no-till (NT), on soil hydraulic properties have been studied in recent decades. In this paper, we incorporated an auto-calibration algorithm into the Soil and Water Assessment Tool (SWAT) model and calibrated the model at eight field sites with soil water content (SWC) observations in the Pataha Creek Watershed, WA, USA. The Green–Ampt method in SWAT was chosen to determine infiltration and surface runoff. Parameter uncertainty was quantified by “relatively optimal” parameter sets filtered by a critical objective function value. Cluster analysis was adopted to obtain equal-sized parameter sets for each site and to compare parameter sets between tillage practices. The centers of these clusters were employed as a sample of parameter values. The clustered parameter sets were then used in scenario analysis to examine the impacts of cropland tillage practices on lateral flow, runoff and evapotranspiration (ET). The model parameters (e.g., soil hydraulic properties) were significantly different between CT and NT. In particular, higher bulk density, larger available water capacity, and higher effective hydraulic conductivity were found for NT than for CT. SWCs at three depths of the NT sites were significantly higher than those of CT sites, which could be attributed to tillage practices. However, higher available water capacity at NT sites indicated that the NT soil had a higher capacity to hold water. Thus the mean net changes in SWC during a year were not significantly different between CT and NT. The statistically different model parameters neither resulted in statistical differences in annual outputs (e.g., runoff and ET) nor substantial differences in monthly outputs. Our study indicates that the tillage impacts on hydrological processes are site-specific and scale-dependent.

Step-pool morphology in high-gradient countersunk culverts

Bed stability and morphology in countersunk culverts on steep slopes were examined to improve understanding of the parameters governing sediment flow characteristics in mountain streams. The knowledge gained was used to provide preliminary construction guidelines for the stream simulation approach of countersunk culverts, an approach that is under consideration in Washington State. Prototype conditions were evaluated in a flume for a 30 percent countersunk culvert with slopes ranging from 3 percent to 7 percent and particle relative submergence varying from 0.5 to 2.0 for three bed size distributions. The experiments were designed to satisfy the conditions of dynamic similarity, and they are preferred to field measurements because they allow a high degree of control over testing conditions. It was found that step-pool bedforms are the most ubiquitous features along the culvert gravel bed. A new formula was developed that correlates step height with the gravel-bed size distribution, relative submergence of the particles, and the Froude number. The step spacing was found to be related to step height and streambed longitudinal slope. This information was combined into a generic design method for streambed simulation of high-gradient countersunk culverts. An example case that illustrates the application of the newly derived formulas to the construction of a gravel bed for a countersunk culvert is provided.

Predicting fish passage design flows at ungaged streams in eastern Washington

Abstract The Washington Department of Fish and Wildlife recently established statewide guidelines for incorporating adult fish migration into culvert design. One of the design options requires an estimate of fish passage design flow for ungaged culvert sites. A new model is presented for estimating fish passage design flows at ungaged sites in Eastern Washington. The model is founded on a unique definition of fish passage design flow and an area-based approach for estimating this flow at ungaged sites. The fish passage design flow was developed by combining the concepts of allowable fish delay, established by fisheries experts to be three days, with a consecutive day analysis. This design flow ensures that fish are not delayed for more than three consecutive days during a water year. A fish passage design flow per unit area is assigned to previously delineated subwatersheds in Eastern Washington using similarity relationships derived from basin parameters and US Geological Survey gaging stations. The percent standard error for this model is 36%, a significant improvement from the 75% standard error calculated for the model previously developed for fish passage design flows in Eastern Washington.

Optimized Petrov-Galerkin model for advective-dispersive transport

Petrov-Galerkin finite element models (PGFEMs) appear to be the preferred choice for simulating advective-dispersive transport of chemicals in the natural environment for their ability to provide oscillation-free results. The PGFEM, however, provides oscillation-free results at the expense of introducing significant artificial dispersion. Introduction of artificial dispersion may lead to erroneous prediction of faster movement of the chemical and underestimation of the peak concentration. The objective of this paper is to develop an optimized PGFEM (OPGFEM). The OPGFEM developed is found to predict advective-dispersive transport of chemicals more accurately than the PGFEM.

Ephemeral gully erosion from agricultural regions in the Pacific Northwest, USA.

Ephemeral gully erosion from agricultural regions in the Pacific Northwest, USA Soil erosion continues to be problematic financially and environmentally with the USEPA ranking sediment as one of the top ten pollutants of concern in the USA. One aspect of erosion often overlooked is the role of ephemeral gullies in terms of quantity of sediment produced and amount exported to nearby waterways. Current physically-based and empirical models are inadequate for predicting this type of erosion particularly at the watershed scale. A new methodology for predicting the quantity and location of sediment delivery was developed and tested via a case study. Aerial ephemeral gully erosion rates varied from 33.6 mton/km2 (0.15 U.S. tons/acre) in the Big Bear Creek basin to 88.4 mton/km2 (0.39 U.S. tons/acre) in the Middle Potlatch Creek basin representing 2.3 to 7.7% of the total surface sediment load. This information was used to develop a predictive Erosion Potential Index (EPI) that uses LANDSAT aerial imagery combined with readily available soils information and a digital elevation model to identify the most probably locations of ephemeral gully development. High resolution aerial imagery was used to quantify actual ephemeral gully locations which were then compared to the EPI predicted locations to verify the procedure. High resolution aerial imagery was also used to quantify the amounts of soil erosion from ephemeral gullies in basins of the Potlatch River system. Krótkotrwała erozja wąwozowa na obszarach rolniczych w północno-zachodnim regionie Pacyfiku, USA W pracy przedstawiono nowa metodykę prognozowania wielkości i miejsc występowania erozji wąwozowej w skali zlewni, którą sprawdzono na podstawie badań przeprowadzonych na obszarze o łącznej powierzchni 736 km2, w sześciu zlewniach mniejszych cieków położonych w środkowej części zlewni rzeki Potlatch. W badaniach wykorzystano zdjęcia lotnicze wysokiej rozdzielczości oraz wyniki pomiarów terenowych parametrów morfologicznych krótkotrwałych wąwozów erozyjnych, na podstawie których stworzono bazę danych GIS. Uzyskane wyniki badań posłużyły do opracowania Indeksu Erozji Potencjalnej (EPI), do określenia którego wykorzystano obrazowania satelitarne LANDSAT w połączeniu z numerycznym modelem terenu oraz dostępnymi informacjami o glebach. W celu weryfikacji procedury wykorzystano zdjęcia lotnicze wysokiej rozdzielczości do określenia ilościowego lokalizacji wąwozów erozyjnych, a następnie porównano z wartościami EPI, wskazującymi przewidywane miejsca występowania wąwozów. Zdjęcia lotnicze wysokiej rozdzielczości wykorzystano również do oceny ilościowej wielkości erozji gleb spowodowanej erozją wąwozową w zlewni rzeki Potlatch.

Global change implications on long-term water supply and demand forecasts in the columbia river basin

The Columbia River Basin (CRB) encompasses parts of seven US states and British Columbia in Canada over a land mass approximately the size of France. It is a vital part of the ecosystem and economies of the entire region. The CRB, like many watersheds around the world, is experiencing increased pressure on water resources and ecosystems, due to population growth, threatened and endangered species, economic development, and climate change. Irrigation is responsible for the majority of consumptive use in the watershed so the implications of climate change are a tremendous concern as we strive to feed a growing population. To facilitate strategic planning and investment, the State of Washington requires a long-term water supply and demand forecast (the Forecast) every five years. An interdisciplinary WSU research team integrated three biophysical models with an agricultural economics model to conduct a system-wide assessment of how future environmental and economic conditions are likely to change water supply and demand by 2030. Timing of supply changes will shift water away from the Sustainable Irrigation and Drainage IV 77 www.witpress.com, ISSN 1743-3541 (on-line) WIT Transactions on Ecology and The Environment, Vol 168,

Water quality and quantity in Jordan's Dead Sea wadis

An evaluation of a potential water supply for the city of Amman, Jordan was conducted for five tributaries (wadis) to the Dead Sea. The total average discharge of approximately 0.85 m3/s (26.8 million cubic metres (MCM)/year) represents a significant quantity of water given the limited fresh-water supplies in the region. Although the raw water concentrations sometimes exceeded allowable concentrations for metals and pathogens, standard drinking water treatment associated with desalination facilities should alleviate most water quality concerns. The total construction cost is estimated to be between

Performance Evaluation of Cold Weather Flow Control and Runoff Treatment BMPs

85 and

CLIMATE CHANGE IMPACTS ON URBAN STORMWATER BEST MANAGEMENT PRACTICES

95 million. Assuming a 15-year design life, this corresponds to a cost of

University student perceptions of the current and future role of non-carbon emitting energy sources in the world

0.22/m3. This is feasible compared to alternative water supply options.