Research methods

Samples from all four sites (Miami, HWY 240, Twin Watersheds and Pristine) are collected when flow is present, such as during spring (snowmelt) runoff and during rain events large enough to produce runoff. The South Tobacco Creek often dries up during extended dry summer or fall periods.

From 1992 to 1996 the land use at the Twin Watersheds two fields were both managed under conventional tillage. Data collected during this period served to provide calibration for research; that is, it allowed researchers to determine differences in runoff characteristics between the two watersheds when under similar land use. In 1997, the East watershed was placed under zero-tillage for the purpose of comparing the differences between conventional and zero-tillage.

The samples were analyzed by Environment Canada for non-filterable residue (sediment), nitrogen, phosphorus, organic carbon and a number of major ions, as well as for pH and conductivity.

This discussion will focus on nitrogen, phosphorus, organic carbon and suspended sediments.

Nutrients, especially nitrogen and phosphorus, have been implicated in eutrophication of lakes. The most significant non-point sources of nitrogen and phosphorus are runoff from urban areas, including industry and transportation, and runoff from agricultural areas. Nutrient inputs from agriculture runoff may originate from commercial fertilizer (inorganic fertilizer) applications and as well as livestock manure and plant material (organic fertilizer).

Total organic carbon (TOC) refers to the amount of carbon in organic material in the water. The main sources of TOC in surface water are photosynthesis, decaying plant and animal material. The TOC concentration has a direct effect on the amount of oxygen in the water.

Nitrogen, phosphorus and organic carbon can be present in either a dissolved form or in particulate form. The percentage of each form is largely a result of natural watershed characteristics, climatic influences and land use activities.

Sediments may originate from the contributing watershed surface landscape or from the stream bank and streambed erosion.

The term "load" refers to the amount of material (weight of nutrient or sediment) transported within a stream, past a vertical cross section within a specific period of time. Load is calculated by multiplying stream flow by substance concentration.

The term "Export coefficients" or unit area load for each element was also determined. In this context, an export coefficient is the amount of a substance (nitrogen, phosphorus, or sediment for example) washed from a hectare of land over the course of one year. Export coefficient calculations were based on the concentration of each substance found in runoff water samples, runoff water volume and hectors within the particular watershed. Rough annual load estimates can be determined in this manner.