Water Quality Management - River Dynamics and Integrated River Management - page 590

Fig. 9.20 Macroinvertebrate biotic index at five sampling locations along Salt Creek from upstream to downstream
as a function of time (data provided by Howard Essig, Illinois Environmental Protection Agency)
municipal and industrial point sources, while Wang (2006) indicated that for Chinese rivers 67% of the
load of total nitrogen and 63% of the load of total phosphorus came from non-point sources. Wang (2006)
further noted the impacts of this pollution as more than 85% of China's lakes are at serious eutrophication
stages and nearly 82% of 532 main rivers in China are contaminated by excessive nitrogen at various levels
(the higher the stream order, the heavier the pollution). It is estimated that the economic loss resulting
from non-point source water pollution in China is 0.5%-1.0% of GDP (Wang, 2006). Water bodies in the
U.S. also are heavily impacted by non-point source pollution with non-point sources impairing 65% of U.S.
streams failing to meet standards and 45% of estuaries (USEPA, 1997b). Thus, this section on nutrient
control focuses on best management practices (BMPs) for the control of nutrients from non-point sources
and the effectiveness of these BMPs.
9.3.2.2 Agricultural BMPs
In a broad sense, BMPs can be defined as any soil treatment, tillage practice, fertilizer-application procedure,
crop rotation, structure, or other practices that achieve some watershed-management goal, such as the
elimination or reduction of flooding, erosion, or transport of pollutants. In this section, however, the
more traditional definition of BMPs as practices used for on-farm soil conservation is used. BMPs for
soil conservation are often hypothesized to be a panacea providing reductions in flooding, erosion, and
nutrient transport. However, the sediment-transport and nutrient-transport mechanisms are substantially
different, and a review of observed nutrient-transport changes for soil-conservation BMPs, considering
these differences, is very important.
This section discusses the principles and performance of one BMP not related to soil conservation,
namely, nutrient management. Nutrient-management practices are included here because when these
practices are carefully combined with soil-conservation BMPs, substantial reductions in nutrient loads
may result.
Soil conservation BMPs include two broad classes: agronomic measures and structural measures. The
agronomic measures can be further subdivided into contour-plowing, strip cropping and vegetative-filter-
strips, and conservation-tillage methods. It is very important to consider that the agronomical and