2018-08-27
The Maitland Valley Conservation Authority has been collecting water samples and promoting Best Management Practices (BMPs) in the Garvey Glenn since 2012. The BMPs are designed to prevent runoff, trap sediment and treat the nutrients to improve the quality of the water.
The type of soil, slope of the land, landuse and climate influence water quality. Areas, such as the shoreline, are naturally vulnerable for poor water quality due to the high potential for runoff the soils and slopes create. Changes over the past 60 years are increasing the runoff potential. Pasture and forage fields now grow corn, beans and grain. Small fields, once separated by fencelines and windbreaks, have become large fields with no fencelines or windbreaks. The changes in the landuse, along with intense weather patterns, have increased the speed at which water, soil and nutrients can run off the land. MVCA has been working with landowners to address runoff from agricultural areas. Improving the water-holding capacity of the soil, planting cover crops and adjusting fertilizer timing and application rates can prevent runoff. Erosion control berms and windbreaks trap the sediment while vegetated areas along the watercourse help treat the nutrients.
Although 5 years of data is not enough to separate the yearly variations in water quality from a statistical trend, we have learned a number of things. Concentrations of nutrients, such as Phosphorus and Nitrate-N continue to be high, high flows are responsible for very poor water quality, the non-growing season is a significant time of year for loadings to occur, and the BMPs are making a difference.
The mean annual concentrations of nutrients in the Garvey Glenn are 2-3 times higher than guideline values for a healthy watercourse. The concentrations are linked to flow, with high flows resulting in high concentrations. In general, half of the flow and loadings occur in winter months (Dec-Mar). The spring (Apr-May), summer (Jun-Sep) and fall (Oct-Nov) contribute approximately 20%, 15% and 15% to the annual flow and loadings respectively. The Garvey Glenn actually stops flowing for a few weeks most summers. Although sources of nutrients can come from multiple sources, including overland runoff, the atmosphere, stream channels and groundwater, the timing of high concentrations in the Garvey Glenn indicate overland runoff is the main source.
Attenuating flows, especially during the non-growing season, is key to improving water quality. Landowners who have installed berms, planted cover crops and are using conservation tillage are reducing runoff and helping to keep soil and nutrients on the land. Computer models, such as the Rural Stormwater Management Model and Soil and Water Assessment Tool, confirm the BMPs are improving water quality. The models highlight the need for a suite of BMPs to match the field conditions. The improvement in water quality however, is difficult to see due to the variability in the data and confounding issues, such as our rapidly changing climate. The MVCA intends to continue collecting water samples and eventually show improvements in water quality as BMPs mature and more are added to the landscape.