What is a hydrologic budget?
A hydrologic budget is the balance of how much water enters a body of water, how much is retained in it, and how much leaves the water body.
Water can arrive from precipitation such rain or snow, inflow from rivers and streams, runoff from the land, and finally from groundwater sources entering from underneath the land. Water leaves by evaporating into the atmosphere or flowing into other waterbodies (in Lake George’s case, that means into the LaChute River and Lake Champlain). Understanding how water arrives into Lake George, how long it stays, and how it leaves is helpful to understanding how to protect it.
How does water enter Lake George?
Lake George is a drainage lake. Over half of Lake George’s water comes from streams. Over 141 streams, shown on the map at right, flow into Lake George, making up 55% of the water that enters the Lake. The rest of the water entering Lake George comes from precipitation (27%) and groundwater (18%).
The sources of a lake’s water supply determine its water quality and are important to consider when choosing management practices to protect that quality.
Lakes like Lake George that receive the majority of their water from streams often have the most variable water quality; water quality depends heavily on the amount and quality of inflow from streams and on human activity in the watershed.
That is one of the main reasons why it is very important to protect the streams and brooks that feed Lake George! the Lake’s Class AA-Special water quality is dependent on receiving clean water.
Eight key streams
Eight major streams supply nearly half of the total amount of flow that comes from that source. They are numbered below and shown on map at right:
- Northwest Bay Brook
- Indian Brook
- Hague Brook
- West Brook
- English Brook
- Shelving Brook
- Finkle Brook
- East Brook.
The retention time of a lake is the average length of time that water remains in the lake. Lake size, water source, and watershed size are primary factors in determining retention time.
The retention time for Lake George is six to eight years. This is very long. Great Sacandaga Lake, a large nearby lake, has a retention time of 0.6 years, while many other Adirondack lakes are flushed in days or weeks.
Why does retention time matter for water quality?
The water in some lakes flushes very rapidly. These short-retention-time lakes respond quickly to management practices that decrease nutrient input.
In contrast, in lakes with long water retention like Lake George, nutrients accumulate and are recycled annually with turnover. In these lakes, the response to management practices that decrease nutrient input is delayed.
How does water leave Lake George?
Lake George drains into Lake Champlain via one source: the LaChute River in the north end.