The importance of understanding stormwater runoff: the major threat to the water quality of Lake George.
Stormwater runoff is widely recognized today as the single biggest threat to the water quality of Lake George. Stormwater runoff occurs during and after a rainstorm or snowmelt, as water flows from building roofs, across lawns, driveways, parking lots, and roads. Changes to land increase stormwater runoff, such as when natural forest is replaced with hard impervious surfaces. These surfaces prevent infiltration and force water to flow over land, collecting pollutants as it makes its way to Lake George. The illustration above shows how stormwater travels over the land surface to Lake George.
Land use activities, such as clearing, excavation and grading, change land characteristics, which then change the natural circulation of water. In undisturbed forest conditions, an estimated 40-60% of rainfall will infiltrate into the ground, 40-50% will be lost through evapotranspiration and 1% will result in surface runoff. (Evapotranspiration is the process of water loss through all parts of a plant, such as roots and leaves.) When a site is cleared and graded, this balance changes to 30% infiltration, 20% evapotranspiration, and 50% in surface runoff.
Although development changes may be small and seem inconsequential on an individual site, the collective effect of increased stormwater runoff from numerous properties throughout the Lake George watershed is substantial. As stormwater runoff increases in volume it carries sediment and soil, as well as nutrients and pollutants, to nearby streams or directly into Lake George.
Local regulations require that no increased stormwater leaves your property after development. A simple principle for landowners is that all stormwater should be treated onsite and as close to where it originates as possible.
Stormwater on Stream Health: Streams play an important role in the watershed. Besides supplying water to lakes and rivers, they provide habitat for a host of both land and aquatic wildlife. During the drier summer months, streams rely on the groundwater, fed through infiltration. But when the infiltration is limited because land use has created stormwater runoff over land, water flow is reduced. The issue is compounded during a storm, when high volumes of runoff flow through the same stream channels, causing undue erosion and the undercutting of stream banks. This can result in flash flooding and alter stream courses. Degraded stream channels supply even more sediment to Lake George.
The cumulative impacts of stormwater runoff in these streams significantly harm aquatic ecosystems. Spawning habitat on rocky stream bottoms are buried in sediment. Increased temperatures from high volumes of warmer stormwater stress macroinvertebrates such as crayfish and insects that other animals rely on for food.
Properly Managing Stormwater: Today, there are effective ways to manage stormwater runoff and protect natural resources, but all too often we fail to implement good stormwater management systems. There are many effective designs and technologies to control stormwater so that it is infiltrated at its source. Yet, stormwater management systems are often poorly understood, under designed or not constructed. The future health of Lake George hinges on our ability to vastly improve stormwater management and treatment throughout the watershed. Many Low Impact Development (LID) practices for improved stormwater control are detailed in Do-It-Yourself Water Quality: A Landowner's Guide to Property Management that Protects Lake George.
Development often changes the hydrology of land so that less is infiltrated into the ground or retained onsite and evaporated, which results in more stormwater flowing across the surface, where it collects nutrients and pollutants, which are then carried to Lake George.
A general rule of thumb is that for properties of one acre or more, two-thirds should remain as natural forests. On properties of an acre or less, one-half should remain as natural forest. The best treatment for stormwater is natural forest and an effort should be made to retain as much as possible.
The most effective way to manage runoff is to capture, infiltrate and treat stormwater onsite so it has the least negative impact on the surrounding environment. Each landowner should strive to retain and treat all stormwater on their property.