The Luckiamute/ Ash Creek watersheds, located near the intersection of five ecoregions, support a rich flora and fauna. Ample resources together with the relatively mild climate and juxtaposition to a major water thoroughfare have made the Luckiamute/ Ash Creek watersheds an important area for human settlement. With their arrival in the Luckiamute/ Ash Creek watersheds thousands of years ago, humans have intentionally and accidentally manipulated and altered many watershed features. Many of the ecological processes that structure and maintain natural resources in the region have also been affected. Today, we see the consequences of these alterations: as the structure and function of the watershed changed, plants and animals had to adapt to the new conditions.
Some species could not adapt and are no longer found in the study area. Populations of other species are currently depressed. For example, valued natural resources in the Luckiamute / Ash Creek watersheds include spring chinook salmon and winter steelhead trout (listed as Threatened (Licata et al., 1998; McElhany et al., 2003) and the Oregon chub is listed as Endangered (Wevers et al., 1992). Many other threatened and endangered plant and animal species are described and listed in Chapter 7 of this report. Wetland and oak savanna communities were also identified as being of concern by the Luckiamute Watershed Council. The persistence of threatened and endangered species depends on proper management of the features in the Luckiamute/ Ash Creek watersheds and an understanding of the ecological processes on which these species depend.
This watershed assessment follows the guidance of the Oregon Watershed Enhancement Board (OWEB); however, there are two important distinctions: (1) the Luckiamute Watershed Council requested that the assessment team include information on terrestrial communities and associated wildlife populations and (2) spatial data were collected, compiled and summarized whenever possible. The goal of this project was to compile existing information to support future action planning and to educate council members. As such, the assessment was meant to summarize current conditions in the watershed using both descriptive and quantitative information and to identify data gaps. Although several example analyses and spatial summaries were performed, this assessment was not intended to identify specific places in the watershed for specific management actions.
In addition to characterizing the status of important natural resources within the study area, the assessment team was charged to provide an ecological context so that members of the Luckiamute Watershed Council could understand the important connections between watershed components, and between watershed components and ecosystem processes. Understanding the relationship between the valued resources and the natural processes that maintain those resources is critical to the development of a successful watershed management plan.
We completed the assessment of the Luckiamute (201,738 acre) and Ash Creek (33,887 acre) watersheds in May of 2004. The study area is located in the Willamette Valley, approximately 62mi south of Portland, Oregon and is located in Benton and Polk Counties. The study area falls within two major (5th field) watersheds. It is bounded on the west by the ridge tops of the Coast Range Mountains and on the east by the Willamette River. Both physical and biological factors affect the quantity and quality of natural resources in the Luckiamute/ Ash Creek study area. Interestingly, humans have influenced both at regional and global scales.
Physically, the interplay between the climate and the geomorphology created and maintain the structure of the Luckiamute/ Ash Creek stream network and the plant communities. The relatively mild climate of the Luckiamute/ Ash Creek study area is characterized by cool wet winters and warm dry summers. The annual mean temperature in the watershed is 51.9?F. Mean summer temperatures range from about 55?F in May to 66?F in July and August. Mean winter temperatures range from about 39?F in December to 42?F in February. Most precipitation falls as rain so that streams and rivers are fed by rainfall rather than snowmelt (Clark, 1999). Seventy-five percent of the annual rainfall occurs between October and March. Elevation profoundly affects precipitation patterns. In the lowlands the mean annual rainfall is approximately 53.0 inches (Oregon Climate Service, 2003). The highest amount of rainfall occurs along the northwestern boundary of the watershed in the Coast Range Mountains where the annual precipitation is greater than 150 inches (Daly et al., 2003; Taylor et al., 2003).
Most of the Luckiamute / Ash Creek study area ranges between 105 to 1,000 feet in elevation. A small proportion of the watershed reaches elevations of 2,000 to 3,650 feet. Rain-on-snow events, important events that structure stream networks and deliver sediments and debris to streams, are relatively rare at the low elevations and
At the local scale, human actions probably do not have much of an effect on climate in the study area; however, many of our actions have changed the quality, quantity and timing of sediment and organic debris delivery to the stream network. Intentional fires were set in the lowlands by Native Americans to clear underbrush and promote game production. Fires probably burned through wet shrubby areas and removed stream side vegetation, and added ash to streams and rivers. It is difficult to say what the impact of these fires would have been on fish and wildlife populations at the time.
However, major, persistent alterations to streambeds and riparian areas occurred as the area was settled by European settlers. Settlers cleared the lowlands for agricultural (and livestock) uses. Streams and rivers were cleared of debris jams for navigation. Splash dams were built to transport lumber from the upper watershed to the river transportation corridors. Historic records indicate that there were from 80-100 splash dams on the Luckiamute River (Licata et al., 1998) with some major ones documented on Pedee Creek and Ritner Creek (Theurer, 2003).
The condition of the stream channels is not well known in the Luckiamute/ Ash Creek study area. A recent report describes nearly all stream channels in the study area as being incised and disconnected from their floodplain. The impact on in-stream biota is one where water velocities are typically much greater, over larger areas than they were historically. Stream network simplification has perpetuated the cycle of increased downcutting and increased stream bank erosion. Consequently, floodplain water storage has been reduced leading to a reduction in summer baseflows and a degradation of water quality. We found that only 12% (of the 1:100K stream length) of the streams in the study area have been surveyed by Aquatic Habitat Inventory (AHI) crews and some of the surveys are more than nine years out of date. We used ODFW benchmarks to evaluate stream segments for each of the 7th field subbasins surveyed by AHI crews. Of all the 12 7th field watersheds, only Lower Pedee Ck (#17090003060401) ranks high in terms of desirable pool characteristics although, like the other basins, none of its stream reaches meet ODFW benchmark criteria for distance between pools.
We also evaluated AHI data for each of the 7th field watersheds using the ODFW habitat benchmarks for key pieces of large wood, number of large wood pieces and large wood volume. Numerous debris jams have been observed by residents of the Luckiamute/ Ash Creek watershed yet AHI surveys show that overall, large wood is scarce in the stream reaches surveyed. Only two of the 7th field watersheds have any stream reaches that meet the desired criteria for key pieces of large wood. Several of the watersheds have stream reaches that meet desirable benchmarks for the number of pieces and large wood volume, but over all the majority of habitat surveyed falls into the undesirable category. Upper Pedee Ck (7090003060402) stands out as having the highest proportion of stream reaches meeting the desirable criteria for large wood. These results suggest that an important component of ‘salmon habitat’ is missing or severely compromised over much of the study area. Action planning should focus on improving in-stream habitat quality by reconnecting floodplains and adding structural complexity to the streams.
Ecosystems are dynamic. In developing a restoration and management strategy, it is important to consider the current status of the resource and the natural range in variability of that resource. In the case of large wood in streams, the Watershed Council must reconcile what they ‘know’ to be true for the amount of large wood in streams with what the natural range in the amount of wood should be (ODFW benchmarks can be used). This will undoubtedly be accomplished through a standardized survey, i.e., AHI surveys or aerial photography. Part of the management
strategy for maintaining in-stream complexity (large wood) should include natural wood recruitment. Wood enters stream networks from the upper watershed (‘hollows’ or ‘zero-order’ streams) and from the riparian area. As part of this assessment, we used aerial photographs to characterize riparian areas throughout the Luckiamute/ Ash Creek watersheds.
Riparian areas (defined as 100ft on either side of the stream) in the Luckiamute watershed are dominated by dense conifer forests (43.5% of the riparian zone) and dense deciduous forests (19.4% of the riparian zone). About 18.4% of the riparian zone is herbaceous land cover indicating that there may be ample opportunity for stream side planting wherever appropriate. In contrast, the Ash Creek watershed is dominated by herbaceous cover (45.3% of the riparian zone) and only 13.5% and 12.9% of the riparian zone is covered with dense coniferous and deciduous forests, respectively. For the areas that were surveyed by AHI crews, we found that none of surveyed stream reaches met the ODFW-benchmarks for riparian conifers and that most of the streams were unshaded by trees within 12m of the stream edge. Short-term management planning may involve placing wood in streams to increase in-stream complexity that has been removed or degraded while not adding to the major debris jams that are known from some areas. However, stream complexity is the result of interactions between water and the landscape. Long-term management strategies should include management for peak hydrologic flows (i.e., increasing watershed water storage and desynchronizing peak flows) and managing vegetation in ‘zero-order’ streams and along riparian areas to promote natural recruitment of large wood to streams.
Land cover and vegetation also affects the way in which a watershed functions. For example, large conifers in the fog zone can cause atmospheric moisture to condense, flow down the branches and tree trunk and eventually into streams. And, living and dead vegetation acts as a giant sponge, holding water thereby increasing watershed water storage. There have been dramatic changes in the quality and distribution of plant communities in the study area primarily due to human alterations.
Analysis of the Pacific Northwest Ecosystem Research Consortium (PNERC) pre-settlement vegetation layer indicated that the coniferous forests dominated the western, higher elevations of the watershed and a large area along the south central boundary of the Luckiamute/ Ash Creek study area. Coniferous forests covered approximately 31.9% (76,000 acres) of the study area. Interestingly, prior to European settlement, shrubby areas were just as common as coniferous forests. Upland and wetland shrubby areas covered much of the eastern, low areas in both the Luckiamute and Ash Creek watersheds covering about 76,114 acres (32.0% of the study area). Much (53,674 acres or ~22.5% of the study area) of the remaining area was dominated by herbaceous plant communities, wet prairies and natural grasslands. Mixed and deciduous forests (which included Oak Savanna) covered 7.3% and 5.8% of the study area, respectively.
To compare past with present land cover, we summarized the PNERC LULC_90 (LULC is Land Use Land Cover) data set. We combined 60 original cover classes into nine major cover classes (and a background class). Surprisingly, we found that coniferous forests also dominate the current Luckiamute and Ash Creek watersheds, covering 32% (~76,153 acres) of the study area. Current coniferous forests cover approximately the same extent as pre-settlement coniferous forests. The largest change in land cover has been in the shrub cover classes, which have decreased by approximately 24% since the time of European settlement. Shrubby communities include shrubby wetlands and riparian areas, as well as field-forest transitional communities. Herbaceous land cover classes are currently a dominant feature, the
second largest cover class, in the Luckiamute / Ash Creek watersheds covering about 30% (70,623 acres). Originally, native grasslands only accounted for approximately 5% of the watershed area prior to European settlement. Native grasslands have been replaced by cropped fields and pastures. Although it is tempting to suggest that the coniferous forests have remained pretty much the same and that shrub communities have been replaced by herbaceous communities, the distribution and composition of forests, shrub and herbaceous communities have changed across the Luckiamute/ Ash Creek study area.
The quality of land cover and plant communities has changed as well as the quantity. Although it is not possible to say for certain, the distribution of the major vegetation cover classes has apparently changed in the Luckiamute/ Ash Creek watersheds. We do know that the landscape has become more fragmented by roads and development than it was prior to European settlement. These changes have undoubtedly had an effect on the delivery of water, sediments, and debris to the stream network and on the way in which fish and wildlife use and move through the study area watersheds. The composition of the plant communities has changed also as non-native and pest plant species have become established in the study area. Lists of non-native and invasive plant species are currently being complied by at least two separate groups for the study area; however, the affect of these non-native species on the structure and function of the watershed are not known.
Wetlands perform numerous ecological roles including water storage, improving water quality, providing food and shelter for many types of fish and wildlife species. Wetland maps were not available for the entire study area; however, we estimated the change in wetland area for each 7th field watershed from pre-settlement to modern times. In the Luckiamute watershed, we found that generally 0-32% of the original wetland acreage remains, while in the Ash Creek watershed 2-63% of the wetlands remain (except for the American Bottom 7th field watershed, which has 95% of its original wetlands remaining). Future action planning and management should include the restoration of wetlands because increasing the amount of wetlands will likely increase watershed water storage, improve water quality, and may provide important fish and wildlife habitat.
In addition to changing the composition and the distribution of plant communities in the Luckiamute/ Ash Creek watersheds, the increasing human population has dramatically affected the quality and quantity of water available in streams for use by fish and wildlife. In 2002, approximately 32 miles of the Luckiamute River appear on the 303(d) list. The Luckiamute River was listed in 1998 for fecal coliform bacteria concentrations that exceeded the water quality standards for water contact recreation. Approximately 17 miles of Soap Creek are listed for not meeting the dissolved oxygen concentration water quality standard from October through May. Soap Creek was listed in 2002 and salmonid spawning was the beneficial use that was impaired. Finally, approximately two miles of the South Fork of Berry Creek were listed for temperature in 2002. Stream water temperature exceeded the state water quality standards (17.8oC) for salmon fish rearing. Both salmonid fish rearing and anadromous fish passage are the beneficial uses that were affected.
We also reviewed water quality data collected by various agencies and stored in the
ODEQ LASAR and US EPA STORET databases. We found it difficult to draw conclusions from these data because measurements tended to be made at irregular intervals and at widely separated monitoring stations. Results of several intensive studies were also available. Unfortunately, these studies occurred under drought conditions and were thought not to be representative of conditions in the watershed.
Western Oregon is known for its abundant precipitation. However, both surface and ground water supplies are heavily used in the Willamette Valley and there frequently is not enough water to meet water demands. There are almost 1,000 unique surface water withdrawal permits in the study area. Approximately 59% of the surface water used in the study area is for irrigation and an additional 17% to water livestock. About 16% of the current surface water use is for domestic, municipal and water storage use. Most of the streams in the watershed are fully appropriated for summer and early fall use; that is, the streams will not support additional water withdrawal for use at these times.
Most (85-90%) of the land in the study area is privately owned. Therefore, action planning will rely heavily upon the cooperation and participation of willing landowners. The statuses (e.g., population size) of many of the valued resources are not well known; however, many factors that affect these valued natural resources have been identified. Many of these factors, e.g., climate, land cover/ land use, habitat fragmentation, water quality, hydrologic patterns, erosion, urbanization, and stream channel modification have been summarized in this report. We have identified many
data gaps. Action planning should focus on management actions that (1) quantify valued resources and (2) restore important ecological processes to their natural range variability and break trends in cycles of resource degradation. Above all else, management and restoration plans must balance the needs of the more than 150,000 people living in Polk and Benton Counties with the needs of the plants and animals of the Luckiamute / Ash Creek watersheds.