Northwest Watershed Research Articles

Unearthing the legacy of wildfires: post fire pyrogenic carbon and soil carbon persistence across complex Pacific Northwest watersheds

Wildfires have the potential to dramatically alter the carbon (C) storage potential, ecological function, and the fundamental mechanisms that control the C balance of Pacific Northwest (PNW) forested ecosystems. In this study, we explored how wildfire influences processes that control soil C stabilization and the consequent soil C persistence, and the role of previous fire history in determining soil C fire response dynamics. We collected mineral soils at four depth increments from burned (low, moderate, and high soil burn severity classes) and unburned areas and surveyed coarse woody debris (CWD) in sites within the footprint of the 2020 Holiday Farm Fire and in surrounding Willamette National Forest and the H.J. Andrews Experimental Forest. We found few changes in overall soil C pools as a function of fire severity; we instead found that unburned sites contained high levels of pyrogenic C (PyC) that were commensurate with PyC concentrations in the high severity burn sites—pointing to the high background rate of fire in these ecosystems. An analysis of historical fire events lends additional support, where increasing fire count is loosely correlated with increasing PyC concentration. An unexpected finding was that PyC concentration was lower in low soil burn severity sites than in control sites, which we attribute to fundamental ecological differences in regions that repeatedly burn at high severity compared with those that burn at low severity. Our CWD analysis showed that high mean fire return interval (decades between fire events) was strongly correlated with low annual CWD accumulation rate; whereas areas that burn frequently had a high annual CWD accumulation rate. Within the first year postfire, trends in soil density fractions demonstrated no significant response to fire for the mineral-associated organic matter pool but slight increases in the particulate pool with increasing soil burn severity—likely a function of increased charcoal additions. Overall, our results suggest that these PNW forest soils display complex responses to wildfire with feedbacks between CWD pools that provide varying fuel loads and a mosaic fire regime across the landscape. Microclimate and historic fire events are likely important determinants of soil C persistence in these systems.

Precipitation, topography, and soil conservation measures determine the spatiotemporal pattern of sediment yield at the regional scale

Exploring the driving effects of control factors on changes in sediment yield from a watershed perspective is of paramount importance for refined watershed management. The objective of this research is to unveil the spatiotemporal variation of sediment yield in the Coarse Sandy Hilly Catchments (CSHC) region from 1956 to 2019 and further investigate the relationship between sediment yield and driving factors. The findings revealed that the mutation years of sediment load (SL) at Toudaoguai and Longmen stations were 1986 and 1996, respectively, with annual SL declining by 66.75 % and 79.04 % after the mutation. Water and sediment discharge at Toudaoguai station exhibited more consistent fluctuations over time, while water and sediment discharge at Longmen station remained relatively consistent before 1967, followed by an entirely inconsistent trend. The spatial pattern of the annual average specific sediment yield (SSY) indicated that the northwest watersheds had a relatively higher erosion rate compared to the southeast. Over time, the SSY of each watershed exhibited a decreasing trend. The SSY showed significant negative correlations with terrace, afforestation, topographic position index (TPI), grass planting (GP), and elevation, while demonstrating significant positive correlations with rainfall indicators and runoff depth. Changes in precipitation, topography, vegetation and engineering measures accounted for 58.5 % of the variance in SSY. The total impact of precipitation on SSY change was positive (standard path coefficient (SPC) = 0.567, P < 0.01), whereas the total impact of topography, vegetation measures, and engineering measures on SSY change was negative (SPC = -0.282, −0.231, and −0.087, respectively). This study quantified the impact of different types of controlling factors on sediment yield at the watershed level. The insights provided by these results can contribute to sustainable watershed management and the optimal allocation of soil and water conservation measures (SWCMs).

The invertebrate host of salmonid fish parasites Ceratonova shasta andParvicapsula minibicornis (Cnidaria: Myxozoa), is a novel fabriciid annelid, Manayunkia occidentalis sp. nov. (Sabellida: Fabriciidae).

Myxosporea (Cnidaria: Myxozoa) are common fish parasites with complex life cycles that involve annelid hosts. Two economically important salmonid-infecting myxosporeans from rivers of the northwestern United States, Ceratonova shasta (Noble, 1950) and Parvicapsula minibicornis Kent et al., 1997, have life cycles that require a freshwater annelid host, identified previously as Manayunkia speciosa Leidy, 1859. This species was described originally from Pennsylvania, with subsequent records from New Jersey, the Great Lakes and west coast river basins. Despite apparent widespread distributions of both suitable fish hosts and the nominal annelid host, both parasites are restricted to river basins in the northwestern US and have never been recorded from the Great Lakes or the eastern US. In this study, we sampled 94 infected and uninfected annelids from two northwestern US rivers to confirm the identity of the host. We found these new specimens had mitochondrial COI sequences with no more than 4.5% distance from each other, but with at least 11% divergence from M. speciosa sampled from near the type locality (New Jersey) and Lake Superior. We did not recover any M. speciosa from either west coast river. The annelid from the Klamath and Willamette rivers showed marked sexual dimorphism that has not been reported in any Manayunkia described to date, though it is apparent that this had been missed in M. speciosa. Accordingly, we describe a new taxon, Manayunkia occidentalis sp. nov., and show that it can host both C. shasta and P. minibicornis. We suspect that previous records of Manayunkia from Pacific Northwest watersheds are likely to be M. occidentalis sp. nov. and not M. speciosa. Sampling of Manayunkia from additional localities is underway to test if the novel Manayunkia species is the only freshwater fabriciid annelid present across the Pacific Northwest.

Annotated check-list of semi-aquatic bugs of Tunisia, with detailed Faunistic Survey of North Tunisia (Hemiptera: Heteroptera: Gerromorpha)

Abstract During the extensive recent survey, a total of 1655 specimens of Gerromorpha (Hemiptera: Heteroptera) were collected in 51 different localities belonging to five watersheds (Medjerda, North-West watershed, Joumine, Sedjenane, North-East watershed) of the North of Tunisia. Thirteen species belonging to seven genera representing five families were identified. Gerris lacustris (Linnaeus, 1758) and Hebrus montanus (Kolenati, 1857) are new records for Tunisia. The fauna of Gerromorpha from northern Tunisia is provided on the basis of the material newly collected and the collection of the Museum National d’Histoire Naturelle, Paris. All the species of Gerromorpha recorded from Tunisia are catalogued, occurrence of 5 families, 7 genera and 15 species are confirmed, occurrence of two previously recorded species (Rhagovelia nigricans nigricans (Burmeister, 1835), Limnogonus cereiventris (Signoret, 1862) is uncertain and requires confirmation.

Modifying WEPP to Improve Streamflow Simulation in a Pacific Northwest Watershed

Abstract. The assessment of water yield from hillslopes into streams is critical in managing water supply and aquatic habitat. Streamflow is typically composed of surface runoff, subsurface lateral flow, and groundwater baseflow; baseflow sustains the stream during the dry season. The Water Erosion Prediction Project (WEPP) model simulates surface runoff, subsurface lateral flow, soil water, and deep percolation. However, to adequately simulate hydrologic conditions with significant quantities of groundwater flow into streams, a baseflow component for WEPP is needed. The objectives of this study were (1) to simulate streamflow in the Priest River Experimental Forest in the U.S. Pacific Northwest using the WEPP model and a baseflow routine, and (2) to compare the performance of the WEPP model with and without including the baseflow using observed streamflow data. The baseflow was determined using a linear reservoir model. The WEPP-simulated and observed streamflows were in reasonable agreement when baseflow was considered, with an overall Nash-Sutcliffe efficiency (NSE) of 0.67 and deviation of runoff volume (D v ) of 7%. In contrast, the WEPP simulations without including baseflow resulted in an overall NSE of 0.57 and D v of 47%. On average, the simulated baseflow accounted for 43% of the streamflow and 12% of precipitation annually. Integration of WEPP with a baseflow routine improved the model’s applicability to watersheds where groundwater contributes to streamflow.

Seasonal versus transient snow and the elevation dependence of climate sensitivity in maritime mountainous regions

[1] In maritime mountainous regions, the phase of winter precipitation is elevation dependent, and in watersheds receiving both rain and snow, hydrologic impacts of climate change are less straightforward than in snowmelt-dominated systems. Here, 29 Pacific Northwest watersheds illustrate how distribution of seasonal snow, transient snow, and winter rain mediates sensitivity to 20th century warming. Watersheds with >50% of their area in the seasonal snow zone had significant (α ≤ 0.1) trends towards greater winter and lower summer discharge, while lower elevations had no consistent trends. In seasonal snow-dominated watersheds, runoff occurs 22–27 days earlier and minimum flows are 5–9% lower than in 1962, based on Sen's slope over the period. Trends in peak streamflow depend on whether watershed area susceptible to rain-on-snow events is increasing or decreasing. Delineation of elevation-dependent snow zones identifies climate sensitivity of maritime mountainous watersheds and enables planning for water and ecosystem impacts of climate change.

Ekalaka, Montana small watershed data set: Precipitation, runoff, air temperature, and soil water, 1968–1980

A 12‐year (1968–1980) hydrologic database has been developed for three sets of watersheds on the frail land resource area located near Ekalaka in southeast Montana. These records contain daily maximum and minimum air temperature, precipitation, runoff, soil water measured monthly and more often during the growing season, and breakpoint precipitation and runoff for summer runoff events. These data can be accessed from the U.S. Department of Agriculture, Agricultural Research Service, Northwest Watershed Research Center, Boise, Idaho database through the anonymous ftp site ftp.nwrc.ars.usda.gov.

CLIMATIC AND HYDROLOGIC VARIABILITY IN A COASTAL WATERSHED OF SOUTHWESTERN BRITISH COLUMBIA1

ABSTRACT: Climate data from the Malcolm Knapp Research Forest (MKRF) in the Coast Range mountains of southwestern British Columbia were used to examine relationships between climate and hydrology and variations in the El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Air and water temperatures were higher and precipitation was lower during in‐phase or warm PDO/E1 Niño events than in other years. In contrast, in‐phase or cool PDO/La Niña years were generally cooler and wetter than other years. Precipitation and East Creek discharge were positively related to the Southern Oscillation Index (SOI) and negatively related to the PDO index. Conversely, air and water temperatures were negatively related to the SOI and positively related to the PDO index. Differences in precipitation and air temperature were also evident at longer time scales when separated by PDO phase. Because of drier conditions during in‐phase El Niño events, the flow of organic matter from East Creek to downstream portions of the channel network was lower compared to other years. This reduction has implications for downstream communities, as these subsidies provide a major source of energy for stream food webs. Therefore, short term and long term shifts in climate, discharge, and water temperature may have profound impacts on the ecology of Pacific Northwest (PNW) watersheds due to changes in a number of ecosystem processes such as altered flux of organic matter from headwater streams to larger rivers.

A Review of Stream Restoration Techniques and a Hierarchical Strategy for Prioritizing Restoration in Pacific Northwest Watersheds

Millions of dollars are spent annually on watershed restoration and stream habitat improvement in the U.S. Pacific Northwest in an effort to increase fish populations. It is generally accepted that watershed restoration should focus on restoring natural processes that create and maintain habitat rather than manipulating instream habitats. However, most process-based restoration is site-specific, that is, conducted on a short stream reach. To synthesize site-specific techniques into a process-based watershed restoration strategy, we reviewed the effectiveness of various restoration techniques at improving fish habitat and developed a hierarchical strategy for prioritizing them. The hierarchical strategy we present is based on three elements: (1) principles of watershed processes, (2) protecting existing high-quality habitats, and (3) current knowledge of the effectiveness of specific techniques. Initially, efforts should focus on protecting areas with intact processes and high-quality habitat. Following a watershed assessment, we recommend that restoration focus on reconnecting isolated high-quality fish habitats, such as instream or off-channel habitats made inaccessible by culverts or other artificial obstructions. Once the connectivity of habitats within a basin has been restored, efforts should focus on restoring hydrologic, geologic (sediment delivery and routing), and riparian processes through road decommissioning and maintenance, exclusion of livestock, and restoration of riparian areas. Instream habitat enhancement (e.g., additions of wood, boulders, or nutrients) should be employed after restoring natural processes or where short-term improvements in habitat are needed (e.g., habitat for endangered species). Finally, existing research and monitoring is inadequate for all the techniques we reviewed, and additional, comprehensive physical and biological evaluations of most watershed restoration methods are needed.

Geographic Database, Reynolds Creek Experimental Watershed, Idaho, United States

The Reynolds Creek Experimental Watershed (RCEW) exhibits spatial variability typical of the intermountain region. We provide a geographic database to provide continuous spatial coverage of landscape properties that may be useful for distributed hydrological modeling or other kinds of spatial analyses and to provide a spatial context for point measurements that have been part of the long‐term monitoring described in companion papers. All data are available as separate geographic information system (GIS) layers which can be selected independently according to need. The base map for all the RCEW GIS layers is a 30 m resolution digital elevation model. Data are available in either vector or raster format where appropriate via the U.S. Department of Agriculture, Agricultural Research Service, Northwest Watershed Research Center anonymous ftp site ftp.nwrc.ars.usda.gov.

Long‐Term Soil Temperature Database, Reynolds Creek Experimental Watershed, Idaho, United States

We describe long‐term soil temperature data collected at the Reynolds Creek Experimental Watershed (RCEW). These data were collected for over 15 years at five locations representing different climatic regimes and soils in the RCEW. Measurements were made at several depths at each site to a depth of 180 cm in most cases. Each site is located in close proximity to a climate station. Descriptive soil profile information is also available for each site. We illustrate two aspects of the data set, the impact of snow depth on soil temperature and the interannual variability of soil temperature at a site. These data are available to the public via the U.S. Department of Agriculture, Agricultural Research Service, Northwest Watershed Research Center anonymous ftp site ftp.nwrc.ars.usda.gov.

Long‐Term Soil Water Content Database, Reynolds Creek Experimental Watershed, Idaho, United States

We describe long‐term soil water data collected at the Reynolds Creek Experimental Watershed (RCEW). Data were collected for 10–25 years at 18 sites representing different climatic regimes and soils in the RCEW. Soil profile data are also available. High correlation between neutron probe and lysimeter measurements are the basis for assessing the accuracy of neutron probe–measured changes in soil water content. These data are available to the public via the U.S. Department of Agriculture, Agricultural Research Service, Northwest Watershed Research Center anonymous ftp site ftp.nwrc.ars.usda.gov.

Long‐Term Stream Discharge and Suspended‐Sediment Database, Reynolds Creek Experimental Watershed, Idaho, United States

The U.S. Department of Agriculture, Agricultural Research Service, Northwest Watershed Research Center initiated a stream discharge and suspended‐sediment research program at Reynolds Creek Experimental Watershed in the early 1960s. Continuous discharge measurements began at two sites in 1963, at three additional sites in 1964, and at eight additional sites in subsequent years. Contributing areas to these gauging stations range from 1.03 to &gt;23,822 ha, selected to represent the broad range of environmental settings found across northwestern rangelands. Quality‐controlled, validated breakpoint and hourly stream discharge data sets are available for these 13 sites for the period 1963 through 1996 (or for a subset of that time for some sites). Suspended‐sediment data are available for three gauging stations (high elevation, middle elevation, and low elevation). All data are available on the Northwest Watershed Research Center anonymous ftp site (ftp.nwrc.ars.usda.gov).

An Approach to Restoring Salmonid Habitat-forming Processes in Pacific Northwest Watersheds

We present an approach to diagnosing salmonid habitat degradation and restoring habitat-forming processes that is focused on causes of habitat degradation rather than on effects of degradation. The approach is based on the understanding that salmonid stocks are adapted to local freshwater conditions and that their environments are naturally temporally dynamic. In this context, we define a goal of restoring the natural rates and magnitudes of habitat-forming processes, and we allow for locally defined restoration priorities. The goal requires that historical reconstruction focus on diagnosing disruptions to processes rather than conditions. Historical reconstruction defines the suite of restoration tasks, which then may be prioritized based on local biological objectives. We illustrate the use of this approach for two habitat-forming processes: sediment supply and stream shading. We also briefly contrast this approach to several others that may be used as components of a restoration strategy.

Channel type and salmonid spawning distribution and abundance

Consideration of fundamental channel processes, together with map-based and field investigations, indicates that stream channel type influences salmonid spawning distributions across entire channel networks and salmonid abundance within channel reaches. Our analysis suggests that salmonid spawning patterns in mountain drainage basins of the Pacific Northwest are adapted to, among other things, the timing and depth of channel bed mobility. We hypothesize that because the bed of pool-riffle and plane-bed reaches scours to a variable fraction of the thickness of alluvium, survival to emergence is favored by either burying eggs below the annual scour depth or avoiding egg burial during times of likely bed mobility. Conversely, annual mobility of all available spawning gravel in steeper step-pool and cascade channels favors either adaptations that avoid egg burial during times of likely bed mobility or selection of protected microhabitats. Consistent with these expectations, we find that salmonid spawning distributions track channel slope distributions in several west-slope Pacific Northwest watersheds, implying that spatial differences in channel processes influence community structure in these rainfall-dominated drainage basins. More detailed field surveys confirm that different channel types host differential use by spawning salmonids and reveal finer-scale influences of pool spacing on salmonid abundance.

An Approach to the Diagnosis and Treatment of Depleted Pacific Salmon Populations in Pacific Northwest Watersheds

We propose an approach to the development of restoration programs for Pacific anadromous salmon that recognizes the importance of an ecosystem perspective. Important concepts such as habitat complexity and self-organizing capacity of the stock are reviewed. A planning process comprised of six steps is described. The approach includes a comparison of historic and current habitat complexity and connectivity and intrapopulation life history diversity. Uncertainties are incorporated into the planning process through assumptions that are clearly identified. Risk of project failure is determined through a qualitative or quantitative weighing of the critical uncertainties. We emphasize the concept that restoration planning is an iterative process that must be continued after implementation.

Investment Rationale for Range Improvement Practices in Eastern Montana

Evidence suggests that the range livestock industry in the Nortbem Great Plains is not as productive as it should be. Ranchers are not readily adopting tbe range improvement practices tbat researcbers recommend. Therefore, an economic survey of eastern Montana ranchers was conducted to evabtate tbe current status of range improvement practices. Specific objectives were to determine: (1) if range improvement investments were bdluenced by ranch sire; (2) the kbrds of range improvements that were being implemented; (3) the areas where additional research was needed in range improvements; and (4) if stocking rates were brfbtenced by ranch size. It was determined that a majority of the ranchers bad purchased equipment and invested in additional water developments, fencing, and other structural improvements during the previous five-year period. A much smaller percentage bad invested in seeded pastures, contour furrows, fertilizer, and other nonstructural improvements. Although small ranches bad more range improvements developed per unit area, large ranches (401 animal units or more) were investing in range improvements more frequently than smaller ranches. Questionnaires returned from 568 ranchers buiicated that research on range improvement practices should emphasize range seeding. Stocking rate on rangeland was not brfluenced by ranch sire. Eastern Montana is an important livestock producing region. During a 1979 survey, 68 1,300 cattle, including calves, and 215,600 stock sheep and lambs, were counted in 14 eastern counties (Montana Dept. of Agr. 1980). Annual cash receipts from the sale of livestock and livestock products totaled $200,745,700. Studies evaluating range improvement practices have shown that a variety of different improvement practices can increase herbage production in eastern Montana (Black and Reitz 1969, Houston 1971, Wight 1975, Wight et al. 1978, Wight and White 1974). Such range improvement practices can substantially increase livestock production in eastern Montana (Houstonand Urick 1972, Wight et al. 1978) and in other regions (Cook and Jefferies 1963, Kearl 1975, Kearl 1979, Workman and Hooper 1968). Range improvements are “special treatments, developments, and structures used to improve range forage resources or to facilitate their use by grazing animals” (Valentine 1971). Although a wide selection of improvement practices exist, Wheeler (1970) determined that capital expenditures for range improvements in the northern Great Plains were largely limited to water development and fencing. A recent U.S. Forest Service study (Horvath et al. 1978), suggested that land management agencies have also invested most of their improvement funding on water development and fencing. Wheeler (1970) suspected that water and fencing were popular improvements because they allowed the rancher to immediately graze more livestock by improving distribution on the same land base. However, he cautioned that the practice of increasing livestock numbers to use the newly accessible portions of the range could lead to overstocking and be detrimental to the long-term productivity of an area. Authorsare range extension specialist, Montana State University, Bozeman 59717; range scientist, USDA, ARS, 270South Orchard, Boise, Idaho 83705;and professor, Department of Range Science, Utah State University, Logan 84322. This article is a contribution from the Northwest Watershed Research Center, Agricultural Research Service, USD+; Bureau of Land Management, USDI; and Montana State University, Bozeman, m cooperation with the Agricultural Experiment Station, University of Idaho, Moscow 83843. Manuscript accepted April 3, 1984. 2 Nonstructural kinds of range improvements, such as brush control, seeded pastures, and contour furrowing have not been as popular as fencing, water developments, and other structural improvements (Lacey 1981). Their economic benefits tend to be less obvious than those from structural improvements. Although scientists develop and field test range improvement practices, it is the livestock producer who ultimately determines the number and kind of improvements on his ranch. Therefore, an economic survey of eastern Montana ranches was conducted to evaluate the current status of range improvement practices. Specific objectives were to determine: (1) if range improvement investments are dependent on ranch size; (2) the kinds of range improvements that are being implemented; (3) the needs (as perceived by the rancher) in the area of range improvement research; and (4) how the use of range improvement practices could influence stocking rate differences between ranch sizes. To enhance communication between ranchers, agricultural lenders, and range scientists,these issues must be resolved. Better communication is needed among these facets of the range livestock industry to ensure long-term productivity.

Evaluating Soil Water Models on Western Rangelands

The soil profile is an important water storage reservoir within the hydrologic cycle. An understanding of the factors affecting daily soil water status is necessary to increase or modify vegetation or water yields. Many mathematical simulation models have been developed to assess soil water status, but none were found that were specifically developed for use on Western rangelands. The purpose of this report was to test soil water models that appeared to be sufftciently general for adaption to rangeland conditions, to determine if they could provide adequate results, and the level of sophistication required. The 2 models selected for evaluation were the Ekalaka Rangeland Hydrology and Yield Model (ERHYM) developed for use during the growing season on grasslands of the northern Great Phtms,and the Soil-Plant-Air-Water model (SPAW), which was developed for use with cultivated crops in the Midwest. Results indicated that both models could be adapted to produce adequate soil water information under rangeland conditions of southwestern Idaho. Overall, the somewhat simpler ERHYM model produced results more closely aligned to observed values than did SPAW. The lack of a snow accumulation and melt routine in SPAW (which could be added) appeared to be the main source of observed differences. These differences were a function of timing rather than a difference in total soil water at the end of each year, where results for the 2 models were very similar. The soil profile is one of the most important water storage reservoirs within the hydrologic cycle. In arid regions, available soil water seldom exists for more than a few months at a time, because it is rapidly extracted by plant transpiration and soil evaporation. Therefore, very little water ever percolates below plant rooting depth. In more humid regions, the magnitude of infiltrated water may be more than adequate for plant needs, and excess water may percolate into ground water reservoirs. An understanding of the factors affecting the day-today soil water status is important when attempting to increase or modify vegetation or water yields. The time distribution of soil water within the root zone is a complex interaction of many variables related to present and historical climate, plants, and parent soil materials. Hildreth ( 1976,1978) indicated that many mathematical simulations or computer models have been developed to assess soil water status. However, most of these models were developed to satisfy a particular need (i.e., spring wheat yield predictions in the northern Great Plains)and may not represent other crops or locations. None of the models were specifically developed for use on Western rangelands. The objective of this study was to determine if existing models with soil water accounting procedures included, representing different levels of complexity and data requirements, could be adapted to particular Western rangeland conditions. Two models were selected for evaluation based on the following criteria: (1) models appeared to be general enough to be adaptable to range conditions; (2) models had been tested against field data (even though for cultivated crops); and (3) documentation was readily available. The models selected were the ERHYM (Ekalaka Rangeland Hydrology and Yield Model) developed by Wight and Neff Authors are hydrologist and hydrologic technician. respectively. Northwest Watershed Research Center, USDA-ARS. 270 South Orchard, Boise, Ida. 83705. Manuscript accepted February 29, 1984. JOURNAL OF RANGE MANAGEMENT 37(6), November 1984 Table 1. Input requirements for running SPAW and ERHYM soil water balance models. SPAW Model ERHYM Model Initial soil water (or default option) Daily precipitation Daily runoff or SCS curve number Daily pan evaporation Monthly pan coefficient Avg. annual pan evaporation Layer thickness A time interval A soil pressure for tolerance parameter Soil water evaporation parameter Soil freezing dates Root distribution Canopy cover curve Canopy susceptibility to water stress Phenology curve Phenology susceptibility to water stress Moisture-stress curves (as provided) Planting & harvest dates Initial soil water Daily precipitation SCS curve number Daily max & min temperature Daily solar radiation

WATER SUPPLY FORECASTING IN REAL‐TIME1

ABSTRACT: A strategy is developed for making seasonal water supply forecasts in real time. It links the traditional regression based forecasting techniques to real‐time data acquired by systems such as the Soil Conservation Service SNOTEL and the U.S. Bureau of Reclamation Hydromet networks. The concept is based on interpolating between the forecast values obtained by using real‐time data in the forecast equations that bracket the real time. Different interpolation procedures were examined and the procedure for calculating confidence intervals about the forecast estimates is developed. The entire conceptual procedure is demonstrated using data from the Reynolds Creek, Idaho, experimental watershed maintained by the USDA‐ARS Northwest Watershed Research Center in Boise, Idaho.

The Effect of Cattle Grazing on Indicator Bacteria in Runoff From a Pacific Northwest Watershed

AbstractTotal coliform (TC), fecal coliform (FC), and fecal streptococcal (FS) numbers were monitored for 3 years to determine the effect of grazing on the presence of these organisms in runoff from a cattle‐grazed and a nongrazed watershed in the Pacific Northwest. The watersheds were characterized by winter precipitation and summer grazing. Weighted‐average numbers of TC and FS in runoff did not appear to be appreciably different between the two watersheds during the study.Numbers of TC in runoff from both watersheds routinely exceeded 10,000/100 mL. Prolonged absence of grazing animals did not seem to affect number of TC and FS in runoff from the check watershed. Each spring after a period of warm weather and prolonged absence of animals, there were increases in numbers of TC, FC, and FS in the runoff. There was some correlation between recentness of grazing and numbers of indicator bacteria in runoff. However, more than a year after animals were removed from the nongrazed check watershed FC numbers in runoff still exceeded 200/100 mL in many samples, and not until the following year did they drop to &lt; 10/100 mL.Sampling at several locations within the grazed watershed showed that sources of indicator bacteria were well distributed, and as a result were nonpoint after the initial runoff events. Thus, present FC recommendations developed for point‐sources would not apply adequately to grazed land in the Pacific Northwest. Indicator bacteria as presently analyzed would not provide a basis for developing best management practices.