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<br />Research has established some values below which nitrogen and
<br />phosphorus would be limiting to algae. growth. . That value is
<br />.1 mg/l for total phosphorus, and .3mg/l for nitrate and
<br />.6 mg/l total nitrogen. These will vary with different species
<br />and conditions .(4) an<! nutrients can also limit growth.
<br />
<br />Natural sourc~s of nitrogen in a stream include the atmosphere,
<br />vegetation, and wild animal wastes while phosphorus input is pri-
<br />marily geologic and animal waste. The only apparent man caused
<br />sources of nutrients into this watershed would be runoff from the
<br />fiood irrigated rangeland that drains directly into the stream and
<br />reservoir, and pollution from campgrounds. Inspection of the camp-
<br />ground sewage systems revealed no deficiencies. Possibly, dumping
<br />from recreation vehicles and trailers could be occurring but none
<br />was apparent.
<br />
<br />The actual data is tabulated in Chapter V while Figure III presents
<br />the nutrient data in graphical form. Inspection of the data reveals
<br />several items of interest.
<br />
<br />1.
<br />
<br />Phosphorus concentrations are very high and increase drastically
<br />below the Wilderness boundary, However, according to most re-
<br />search, the phosphorus level at the Wilderness boundary is still
<br />high enough so as not to .be limiting to most types of algae.
<br />The phosphorus levels below the W~lderness boundary and in the
<br />reservoir are very high when. compared to other streams in the.
<br />San Juan Basin and seem definitely high enough to provide for
<br />nuisance algae conditions if other limiting factors aren't present.
<br />
<br />2.
<br />
<br />Total nitrogen values increas!! noticeably below the Wilderness
<br />boundary. ,This data corresponds with the total phosphorus data
<br />in that it appears the nutrient input increases heavily between
<br />the Wilderness boundary and the. reservoir.
<br />
<br />3.
<br />
<br />~st of the total nitrogen detected in the two stations above
<br />the reservoir is inorganic, that is, has been converted to
<br />ammonia, nitrites, and nitrates. Nearly half of the nitrogen
<br />in the reservoir and below, however, has remained in the organic
<br />form. This indicates a relatively recent input of nutrients
<br />into the system and corresponds with information provided by
<br />other data.
<br />
<br />4.
<br />
<br />The total nitrogen levels are lower with respect to aquatic
<br />vegetation needs than are the phosphorus levels. Four stations
<br />had levels of total nitrogen in excess of known aquatic vegetation
<br />needs while three of the stations in the reservoir or below did
<br />not. This variation is difficult to explain but indicates that
<br />nitrogen instead of phosphorus maybe a limiting factor in this
<br />situation. Because the beginnings of nuisance vegetation has
<br />appeared, it indicates more nitrogen input would increase the
<br />possibility of further problems.
<br />
<br />7
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