D. C. Goodrich

Push broom microwave radiometer observations of surface soil moisture in Monsoon '90

The push broom microwave radiometer (PBMR) was flown on six flights of the NASA C-130 to map the surface soil moisture over the U.S. Department of Agricultures Agricultural Research Service Walnut Gulch experimental watershed in southeastern Arizona. The PBMR operates at a wavelength of 21 cm and has four horizontally polarized beams which cover a swath of 1.2 times the aircraft altitude. By flying a series of parallel flight lines it was possible to map the microwave brightness temperature (TB), and thus the soil moisture, over a large area. In this case the area was approximately 8 by 20 km. The moisture conditions ranged from very dry, 15%, after a heavy rain. The rain amounts ranged from less than 10 mm to more than 50 mm over the area mapped with the PBMR. With the PBMR we were able to observe the spatial variations of the rain amounts and the temporal variation as the soil dried. The TB values were registered to a Universal Transverse Mercator grid so that they could be compared to the rain gage readings and to the ground measurements of soil moisture in the 0- to 5-cm layer. The decreases in TB were well correlated with the rainfall amounts, R2 = 0.9, and the comparison of Tg with soil moisture was also good with an R2 of about 0.8. For the latter, there was some dependence of the relation on location, which may be due to soil or vegetation variations over the area mapped. The application of these data to runoff forecasts and flux estimates will be discussed.

Climate change's impact on key ecosystem services and the human well-being they support in the US

Climate change alters the functions of ecological systems. As a result, the provision of ecosystem services and the well-being of people that rely on these services are being modified. Climate models portend continued warming and more frequent extreme weather events across the US. Such weather-related disturbances will place a premium on the ecosystem services that people rely on. We discuss some of the observed and anticipated impacts of climate change on ecosystem service provision and livelihoods in the US. We also highlight promising adaptive measures. The challenge will be choosing which adaptive strategies to implement, given limited resources and time. We suggest using dynamic balance sheets or accounts of natural capital and natural assets to prioritize and evaluate national and regional adaptation strategies that involve ecosystem services.

KINEROS2-AGWA: Model Use, Calibration, and Validation

KINEROS (KINematic runoff and EROSion) originated in the 1960s as a distributed event-based model that conceptualizes a watershed as a cascade of overland flow model elements that flow into trapezoidal channel model elements. KINEROS was one of the first widely available watershed models that interactively coupled a finite difference approximation of the kinematic overland flow equations to a physically based infiltration model. Development and improvement of KINEROS continued from the 1960s on a variety of projects for a range of purposes, which has resulted in a suite of KINEROS-based modeling tools. This article focuses on KINEROS2 (K2), a spatially distributed, event-based watershed rainfall-runoff and erosion model, and the companion ArcGIS-based Automated Geospatial Watershed Assessment (AGWA) tool. AGWA automates the time-consuming tasks of watershed delineation into distributed model elements and initial parameterization of these elements using commonly available, national GIS data layers. A variety of approaches have been used to calibrate and validate K2 successfully across a relatively broad range of applications (e.g., urbanization, pre- and post-fire, hillslope erosion, erosion from roads, runoff and recharge, and manure transport). The case studies presented in this article (1) compare lumped to stepwise calibration and validation of runoff and sediment at plot, hillslope, and small watershed scales; and (2) demonstrate an uncalibrated application to address relative change in watershed response to wildfire.

Geographic information systems database, Walnut Gulch Experimental Watershed, Arizona, United States

The geographic information systems (GIS) database complementing the Walnut Gulch Experimental Watershed (WGEW) special section papers in this issue of Water Resources Research is described. Spatial data layers discussed here will be especially useful to modelers interested in simulating the spatial and temporal characteristics of rainfall, runoff, erosion, and sedimentation processes on the WGEW. All data are available as either images or individual GIS data layers (vector or raster format) via the U.S. Department of Agriculture Agricultural Research Service Southwest Watershed Research Center at http://www.tucson.ars.ag.gov/dap/. Standard metadata are provided with attending projection information and restrictions on use.

Impact of recent extreme Arizona storms

Heavy rainfall on 27–31 July 2006 led to record flooding and triggered an historically unprecedented number of debris flows in the Santa Catalina Mountains north of Tucson, Ariz. The U.S. Geological Survey (USGS) documented record floods along four watercourses in the Tucson basin, and at least 250 hillslope failures spawned damaging debris flows in an area where less than 10 small debris flows had been documented in the past 25 years. At least 18 debris flows destroyed infrastructure in the heavily used Sabino Canyon Recreation Area (http://wwwpaztcn.wr.usgs.gov/rsch_highlight/articles/20061 l.html). In four adjacent canyons, debris flows reached the heads of alluvial fans at the boundary of the Tucson metropolitan area. While landuse planners in southeastern Arizona evaluate the potential threat of this previously little recognized hazard to residents along the mountain front, an interdisciplinary group of scientists has collaborated to better understand this extreme event.

Application of a rangeland soil erosion model using National Resources Inventory data in southeastern Arizona

Rangelands comprise a large portion of the western United States. They are important for providing ecosystem services such as sources of clean water and air, wildlife habitat, ecosystem biodiversity, recreation, and aesthetics. The National Resources Inventory (NRI) is a primary data source for ongoing assessment of nonfederal land in the United States, including rangelands, and the data collected during an NRI assessment is typical of rangeland monitoring conducted by managers. This study outlines a methodology for using that type of monitoring data to run a rangeland hydrology and erosion model in order to estimate the relative soil erosion rates across ecosystems located in the American Southwest. The model was run on 134 NRI rangeland field locations with data collected between 2003 and 2006 in Major Land Resource Area 41, the Southeastern Arizona Basin and Range, which is a diverse ecological area of 40,765 km2 (15, 739 mi2) in the transition zone between the Sonoran and Chihuahuan deserts. Results of the study showed that the data collected was adequate to run the model and effectively assess the influence of foliar cover, ground cover, plant life forms, soils, and topography on current soil erosion rates. Results suggested that the model could be further improved with additional measured experimental data on infiltration, runoff, and soil erosion within key ecological sites in order to better quantify model parameters to reflect ecosystem changes and risk of crossing interdependent biotic and abiotic thresholds.

Assessing the benefits of grazing land conservation practices

The Conservation Effects Assessment Project (CEAP) component aimed at assessing conservation on grazing lands was initiated in 2006. “Grazing land” is a collective term used by the USDA Natural Resources Conservation Service (NRCS) for rangeland, pastureland, grazed forestland, native and naturalized pasture, hayland, and grazed cropland (figure 1). Although grazing is generally a predominant use on grazing lands, the term is applied independently of any actual use for grazing. Grazing land is also described as land used primarily for production of forage plants maintained or manipulated primarily through grazing management. It includes all lands having plants harvestable by grazing without reference to land tenure, other land uses, management, or treatment practices. Rangelands comprise approximately 40% of the landmass of the United States, including nearly 80% of the lands of the western states. Much of the rangelands in the west are sparsely populated, and conditions on that land are not well documented over extensive areas. Rangelands provide valuable grazing lands for livestock and wildlife and serve as a source of high quality water, clean air, and open spaces for the benefit of both society and nature. While rangelands occur in every region of the North American continent, they are the dominant…

Techniques for assessing the environmental outcomes of conservation practices applied to rangeland watersheds

Grazing lands are the most dominant land cover type in the United States, with approximately 311.7 Mha being defined as rangelands (Mitchell 2000). Approximately 53% (166.2 Mha) of the nations rangelands (USDA 2009) are owned and managed by the private sector, while approximately 43% are managed by the federal government (USDA NRCS 2011a). The remaining rangelands are owned and managed by tribal, state, and local governments. Information on the type, extent, and spatial location of land degradation on rangelands is needed to inform policy and management decisions on rangelands; however, there is no systematic or coordinated national data-set on status or condition of rangelands for the United States to make informed policy decisions (NRC 1994; Herrick et al. 2010). Rangelands in the west are sparsely populated, and assessments of rangeland conditions have historically not been uniformly conducted across all land ownership classes in any systematic monitoring program. Therefore, it is difficult to assess the current health of rangelands and which areas could benefit from targeted conservation as USDA Natural Resources Conservation Service (NRCS) has recently done for cropland within the Upper Mississippi River Basin (USDA NRCS 2010) and the Chesapeake Bay (USDA NRCS 2011b) through the Conservation Effects Assessment Project…

Cheatgrass invasion and woody species encroachment in the Great Basin: Benefits of conservation

The Great Basin is the largest North American desert, covering more than 49.6 million ha (122.5 million ac), and includes most of Nevada, a large part of Utah, and smaller sections of Oregon, Idaho, and California. Two of the biggest threats to ecosystem stability and integrity in the Great Basin are invasive annual grasses, particularly cheatgrass (Bromus tectorum L.), and expansion of native woody plants, particularly juniper (Juniperus spp.) species and pinyon pines (Pinus monophylla Torr. and Frém. and Pinus edulis Engelm.). An estimated 72% (36 million ha [88 million ac]) of the Great Basin is currently impacted by cheatgrass (Pellant et al. 2004). Pinyon and juniper woodlands currently occupy approximately 22.5 million ha (55.6 million ac) throughout the western United States (Miller et al. 2011). In the Great Basin alone, the occupied area is nearly 7.1 million ha (17.5 million ac), the result of a 125% to 625% increase in tree distribution, much of which occurred in areas where these species were not inherent components of the plant community (Miller et al. 2008). The alteration of native plant communities by these invasive species can increase the likelihood of damaging and dangerous wildfires that change the hydrologic system and degrade…

The AGWA - KINEROS2 Suite of Modeling Tools

KINEROS originated in the 1970’s as a distributed event-based rainfall-runoff erosion model. A unique feature at that time was its interactive coupling of a finite difference approximation of the kinematic overland flow equations to the Smith-Parlange infiltration model. Development and improvement of KINEROS has continued for a variety of projects and purposes. As a result, a suite of KINEROS2-based modeling tools has been developed that can be executed from a single shell. The tools range from the event-based KINEROS2 flash-flood forecasting tool to the continuous KINEROS2-Opus2 (K2-O2) biogeochemistry tool. The KINEROS2 flash flood forecasting tool is being tested with the National Weather Service (NWS). It assimilates the NWS Digital Hybrid Reflectivity (DHR) radar product in near-real time and can simultaneously run ensembles using multiple radar-reflectivity relationships. In addition to simulation of runoff and sediment transport, K2-O2 can simulate common agricultural management practices, plant growth, nutrient cycling (nitrogen, phosphorus and carbon), water quality and chemical runoff. Like any detailed, distributed watershed modeling software, the KINEROS2 suite of tools often requires considerable effort to implement; it is necessary to delineate watersheds, discretize them into modeling elements, and parameterize these elements. This need motivated the development of the Automated Geospatial Watershed Assessment (AGWA) tool. This ArcGIS-based tool uses commonly available, national GIS data layers to fully parameterize, execute, and visualize results from both the SWAT and KINEROS2 models. By employing these two models AGWA can conduct hydrologic modeling and watershed assessments at multiple temporal and spatial scales. A variety of new capabilities have been added to AGWA to configure KINEROS2 inputs to simulate a number of land-management practices or changes (fire, urbanization, and best management practices) as well as incorporate decision-management tools for rangelands. An overview of these tools will be provided.