TRANSPARENCY MEASUREMENTS IN A PRAIRIE STREAM--THE KANARANZI CREEK OF SOUTHWESTERN MINNESOTA AND NORTHWESTERN IOWA

Transparency measurements are an inexpensive and efficient way to estimate suspended load in the field. Programs that use a transparency tube can be tailored to conditions in distinct stream reaches and mobilized in response to specific discharge events. During 2007, 2008, and 2009 more than 600 individual transparency measurements were made at eight separate locations distributed along a 15 mi (24 km) portion of Kanaranzi Creek. The resulting profiles illustrate an upstream increase in transparency consistent with an upstream decrease in suspended load. However, one particular profile has an anomalous upstream decrease in transparency that is the expression of a 2 in (5cm) rainfall event in the headwaters area. Similarly, discharge variations in response to the 2007 spring runoff and to more than ten individual rainfall events, are associated with transparency values that correlate with water level measurements. Numerical modeling and remote instrumentation are useful high tech tools for fluvial geomorphology. However, simple observations made at multiple locations and at critical times also provide invaluable insights. Transparency tube estimates of suspended load are an appropriate technology for environmental monitoring and educational field exercises.