INVESTIGATION OF NITRATE POLLUTION IN THE SPRING RIVER, AR: PRELIMINARY RESULTS OF A SPATIAL-TEMPORAL STUDY

Nitrate pollution may be occurring in the main trunk stream of the Spring River watershed (HUC 110010100) of north central Arkansas.  The Spring River, with 92 km reach, enters Arkansas at Mammoth Spring.  From the spring water flows into the Spring River at 34 million liters per hour at a constant temperature of ~ 15⁰ C.  Because of the amount and constant temperature of spring discharge, three distinct thermal zones, (cold, cool, and warm) develop.  Water was collected at 15 sites within the Spring River using trace metal clean procedures.  Anion and cation composition was measured ion chromatography (DX 120).  Preliminary results indicate that the nutrient chemistry of these three zones is distinct both spatially and temporally.  

Spring River fisheries managers have recorded a decline in the +1 and +2 cohort body size, an apparent decrease in juvenile recruitment within the stocked populations and a complete loss of trout fecundity in the cold thermal zone.   Competition or habitat loss can contribute to both male and female growth stunting and delayed maturity.  With the Spring River resource competition is minimal and the habitat appears to be diverse and intact.  We are assessing the relationship between nitrate pollution and apparent stunting of trout within the river. 

The preliminary results of a spatial-temporal study of nutrients in the Spring River are presented.  Historical data (STORET) indicate significant variability in nutrient concentration related to seasonal changes in run-off.  Superimposed upon these seasonal variations are spatially significant variations in nitrate.  Land use patterns along the river are mainly residential.  Agricultural use is dominated by pasture farming away from the main tributaries.  However feeder ditches may drain into ephemeral stream tributaries.  We suspect that the run-off contribution to the nutrient load in the Spring River is supplemented by significant nitrogen input from the spring itself.