Assessing Septic Field Inputs in Watersheds

Session: Finger Lakes Water Quality (2)

Paul Richards, The College at Brockport, [email protected]
Nicole De Rose, The College at Brockport, [email protected]
Marine David, The College at Brockport, [email protected]

Abstract

Nutrient inputs from septic systems is thought to be a significant problem for many Finger Lakes watersheds.  It is challenging to deal with in watershed planning because there is not much information on the spatial distribution of septic systems, and the impact of individual systems is hard to quantify at the watershed scale.  In this study we map septic system leach fields directly using Oblique Imagery and have conducted water quality surveys in stream segments to determine if septic field density is correlated with waterquality.  The study was conducted in Oak Orchard watershed.  A total of 1217 systems were mapped in the watershed.  Septic field density was calculated in 200 meter riparian corridors in a suite of first and second order tributaries.  The segments were sampled for Nitrogen, Phosphorous, and Optical Brighteners. A weak positive (but statistically significant) relationship was found between Dissolved Nitrate and Septic Field Density.  The probability of detecting the presence of optical brightener was positively correlated with the number of septic fields located within 200 meters of the sampling site.  The results suggest that stream waterquality is impacted by septic systems during lowflow conditions, and that systems can be mapped for watershed planning purposes.