Patterns Affecting Water Quality 
i 
Water quality and aquatic life are intimately related to land 
cover near streams. The vegetation near streams is 
referred to as riparian vegetation. It forms an important 
buffer zone protecting water quality. Natural vegetation 
absorbs agricultural nutrients, slows the rate of water 
movement, and is a settling zone for soil particles sus¬ 
pended in runoff. Riparian conditions are often evaluated 
within a few meters of a stream, but the larger landscape 
context is also important. 
One way to measure environmental conditions is to look at 
whether streams flow through predominantly forested or 
developed landscapes within a watershed. If there are no 
large urban areas or agricultural zones anywhere near 
<h 
streams, then it is less likely that water quality is being 
affected by these land uses. If forest cover dominates in 
the vicinity of streams, then there is greater opportunity 
for forests to buffer the conditions within streams. 
Watershed rankings of the proportions of stream length 
dominated by different land cover types are shown in 
Figure 2.7. These proportions are based on forest cover 
(Figure 2,7a) or urban and agriculture cover (Figure 2.7b) 
within about one-half kilometer of streams in each water¬ 
shed. Along the Mississippi River, the rankings for 
forested riparian zones show a sharp contrast between 
the area near the river and the forested areas to the east 
and west. The Tensas River Basin is one of the areas 
near the Mississippi River. 
(f> 
o "o 
i_ <i> 
0) 
J5 £ 
El 
3 ro 
Total Stream Length - Forested 
Tensas River Basin 
National Rank 
Quintile Data Range 
Indicator Ntelue 
Figure 2.7 
Proportion of total stream length that is: (a) forested, or 
(b) agriculture and urban. 
