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The pollutants addressed in this document are heat and fecal bacteria with E. coli as the indicator.

1.4.7.1 Causes

Temperature. Human-related summer heating in the Basin is primarily due to nonpoint source (widespread) heating. Using computer simulations, nonpoint source solar heating was evaluated by comparing the existing vegetation and channel with an estimate of undisturbed conditions. Substantial solar heating occurs due to the combined effects of reduced riparian vegetation height and density and increased channel width, caused by human-related activities. Diminished instream flow contributes to high temperature as well, particularly in July and August as flow approaches the annual minimum, surrounding temperatures are high and solar radiation is relatively direct – and irrigation crops need ample water.

Solar radiation is the energy source driving daily stream heating. Solar radiation is directly influenced by channel and vegetation conditions as stated previously. In addition, streams manifest indirect causes of solar heating. Stream straightening can be an indirect cause of solar heating. Straightening increases gradient, in turn increasing velocity and associated erosivity. This typically enlarges the channel, resulting in a wide and shallow stream, particularly during the low flow season. Bank weakening, by vegetation disturbance and associated loss of soil/root strength, similarly results in wide and shallow channels. Bank disturbance by livestock, vehicles and development generally leads to increases in stream width. A wide shallow stream is readily heated by the sun if not shaded. These situations are common in the John Day Basin, as elsewhere.

In addition, ground water provides thermal moderation. Summer daily temperature increases are less when ground water interacts with streams. The subsurface zone of water exchange between ground water and a stream is called the hyporheic zone. This zone, along with net ground water input to the stream, absorbs heat and directly cools stream water via mixing (in the summer subsurface water is generally cooler than stream water). Common causes of decreased groundwater input and exchange are less floodplain area to collect spring floodwater, decreased sinuosity and associated reduction in bank area to transmit pore water, incision-lowered water tables, well withdrawal and decreased vegetative trapping and storage of precipitation and floodwater. The type, amount and location of crop irrigation often influence groundwater patterns as well. In the John Day Basin, channel and floodplain

modifications that contribute to loss of groundwater-stream interaction include loss of channel complexity. Channel complexity typically includes pool frequency, sinuosity, large woody debris and other attributes. Enabling sinuosity, wet meadows, large woody debris and floodplain area and connection will ultimately provide for a natural channel form with increased groundwater interaction and decreased channel width for solar heating.

Because channel form provides important thermal control, erosion control should be addressed as well. Increased fine sediment loading is generally detrimental to channel form, typically leading to widening and shallowing of the stream. Excess fine sedimentation in streambeds results from excess erosion (upland and channel) and altered stream hydraulics. Stream straightening, bank disturbance, riparian and upland

OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY 54 land cover disturbance are common causes of accelerated erosion. Watershed capture/funneling by road emplacement commonly exacerbates erosion. Best management practices for erosion control are

effective and readily found in watershed literature.

Area climate is another important stream temperature control; though one not subject to locally based human influence. The expected changes coming to the region‘s climate underscore the importance of protecting and restoring the mechanisms that help keep stream temperatures cool. The thermal regimes of streams are expected to change in response to reduced summer stream flows, and increased air temperatures. Climate change can influence vegetation and shade patterns as well.

Stream temperature improvements obtained by growing mature riparian vegetation corridors along stream banks, reducing channel widths, and enhancing summer base flows will help mitigate the expected stream heating resultant from climate change. While some numeric objectives of the TMDL may not be attainable due to factors such as climate change, the general goal remains – natural thermal conditions, given the climatic conditions of the future.

Changes in stream temperature associated with global and regional climate change may require further modifications to the human-source allocations at some time in the future.

E. coli. Bacteria sources generally include livestock, pets, septic and sewer systems and wildlife. In

addition to sources, transport mechanisms are important in addressing bacterial inputs to streams. For instance, high bacteria levels in a field would generally not lead to instream excesses if runoff were controlled by slope, detention or effective buffers. Transport mechanisms include ditches, roads, tributary streams, sewer systems, field and slope runoff and direct deposition.

Natural sources of fecal bacteria include those sources associated with wildlife (non-domestic animals, such as deer, rats, raccoons, ducks, geese and others that live or feed near or in surface waters. For the purposes of TMDL implementation, natural background is generally not targeted for reduction.

1.4.7.2 Management Roles

Land use categories with activities that influence channel and vegetation structure include agriculture, forestry, urban and transportation. As discussed in Section 1.4.4.1, agriculture comprises the largest area of land use in the Basin. Forestry and other forest land uses are the other predominant land uses. Roadways are commonly close enough to constrain channels or limit vegetative shading, as well as contributing to upland erosion. Artificial channel constraints can lead to increased bank and bed erosion and associated channel widening. The area of urban development in the Basin is quite small. Each category of land use has a legacy of vegetation removal/alteration, channel modification and increased erosion, leading to increased stream heating and fine sediment deposition. That said, each land use sector is actively involved with water quality protection and enhancement as well and we at DEQ promote best management practices to enable land uses to meet water quality objectives. We also recognize that part of the difficulty in achieving water quality standards relates to decades-old legacy impacts to the Basin. Planning processes should inventory these issues and we will support the various participants in achieving resources to address them.

Water management plays an important part in water quality in the John Day Basin and throughout the western US. The primary cause of unnaturally low stream flow in the John Day Basin is irrigation withdrawal. While DEQ is not the regulatory agency for stream flow in Oregon, we encourage and will work with OWRD and irrigators in implementing, as feasible, instream flow restoration (further discussion can be found in Section 2.1.3.5).

Agriculture, through livestock operations, close association with water, and its land area predominance, is the land use most associated with above-natural fecal bacteria input to streams, as well as nutrient loading. This is reinforced by stream data indicating high bacterial concentrations where the sole land use

OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY 55 is agriculture, such as above Prairie City on the John Day River. While natural sources are also present along this reach and above it, bacteria concentrations above the area of agricultural land use are low. Bacteria measurements in forested areas in and near the John Day Basin, indicate forest bacteria contributions are slight, though forest sample sites are few in number in the Basin. In forested areas, high levels of fecal bacteria, if occurring, usually will be associated with inadequate waste disposal by recreational users, the presence of livestock or other animals in the stream channel or riparian zone, and poorly maintained on-site treatment systems.

Urban areas are likely contributors of bacteria – through runoff, sewer and storm water systems. However, Basin urban areas are small and excessive bacteria loading is observed above urban areas. Wastewater treatment plants are addressed through permits, and cities are encouraged to assess their source potential and apply standard urban best management practices.

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