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 nitrate concentrations were approximately 1 mg/l with the highest peak level at 4.0 mg/l. Buffer strips
that were not fertilized were effective in keeping losses to less than 0.5%.
Streamside management zones can be an important part of a system to reduce nutrient losses
and provide other water quality benefits (e.g. streambank stabilization, wildlife habitat preservation) .
Management objectives determine SMZ design, however trapping sediment and sediment-attached
pollutants are likely for NPS control. Primary factors for SMZ design are width (length of flow), extent
along water courses and BMPs within the SMZ.
Streamside management zone width is based on slope and soil erodability, and as each of these
increase, proper design width generally increases. Nutter and Gaskin (1989) suggest that soil infiltration
capacity will greatly affect nutrient trapping. Fine soil particles will also travel further, making soil
textural properties important for design (Hewlett 1982).
Since most forest erosion occurs through channelized flow and not sheet flow (Brown, 1980)
the SMZ should protect perennial, intermittent, and ephemeral streams where forest activities increase
upland water runoff. Harvesting can increase water runoff and cause intermittent streams to become
perennial (Lynch et al. 1985).
Partial harvesting within the SMZ is recommended to remove on-site nutrients, encourage stand
growth, and increase nutrient uptake. Omernik (1981) and Fail (1987) found nutrient uptake in a
mature stand is significantly less than one in earlier stages of growth.
Lanier (1990) reports that published literature on SMZ effectiveness for trapping nutrients is
lacking. Recommendations for SMZ design are based on experience and very little monitoring.
Therefore, careful management to reduce NPS impacts will employ SMZs in a system with silvicultural
source controls rather than counting on the SMZ trap pollutants and protect the water course.
Agriculture . The lessons learned from the Model Implementation Program (MIP), the Great
Lakes 108a projects, and the Rural Clean Water Program (RCWP) provide a strong basis for
improving agricultural NPS control methods on a watershed scale.
MIP projects found they should identify and treat critical areas that directly contribute to water quality
results. Five of the MIP projects demonstrated from field and plot studies that BMPs could provide
water quality benefits (NWQEP 1989).
The 108a projects found that conservation tillage was effective at reducing erosion and total
nutrient concentrations however it may increase dissolved nitrogen and phosphorus concentrations in
surface waters, demonstrating the need for nutrient management (Newell et al. 1986). Conservation
tillage and fertilizer management were the most cost effective methods for cropland phosphorus control.
Projects should address the differences in pollution sources to increase the chances of meeting goals.
4.2-9
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