The Water Cycle
What affects streamflow?
To protect the river and its natural communities we need to understand the factors that affect both streamflow and water quality--which are inextricably linked. And we need to understand the effect of human use and development on the watershed. Naturally, some of these things we can control and some we cannot. We'll focus here on the things we can influence and provide links to sources of more general information. Loss of natural flow, is a threat facing both the Assabet and Sudbury Rivers.
Precipitation and climate disruption - the largest single factor in streamflow is precipitation. It affects streamflow immediately through stormwater runoff, and in the longer term, by refilling ("recharging") the watershed's aquifers. According to studies of climate change impacts in the Northeastern United States by the Union of Concerned Scientists, the amount of precipitation on extreme wet or snowy days in winter is likely to increase, while the frequency of extreme hot days in summer will also increase. This is likely to compound the stresses of increasing development and water withdrawals on our streams and rivers. Although we can't change rainfall, we can work to conserve water (especially during times of drought) and we can work to reduce our carbon emissions. Read more about climate change.
Groundwater / surface water interactions - Most people are familiar with the cycle of surface water - the water we can see in the rivers, lakes, oceans, rain, and snow. But what goes on where we can't see it - the groundwater flow - completes the cycle. Take a tour of the groundwater cycle. Use the next page and previous page buttons on the bottom of each page to read through all the pages.
Flow alterations - such as those causes by dams (both man-made and the "natural" ones engineered by the beaver population in the watershed). Read about the dam and sediment study of the Assabet River done by the Army Corps of Engineers. Read more about our work on river restoration and dams.
Water use and water balances - the balance between water withdrawn from the aquifers of a watershed and the water returned to that watershed (as opposed to lost to evaporation) affects both streamflow and water quality. Read about water use, water balance, or computer modeling of groundwater flows.
Point-source pollution - discharges of wastewater from municipal and industrial sources directly affects water quality. Read more about the point-source pollution problems on the mainstem Assabet River.
Land use changes - development in the watershed brings with it a cascade of changes to the natural water cycle. Water that runs rapidly off paved and other impermeable surfaces doesn't have a chance to percolate through the ground to refill the aquifers that we depend on for water supply and baseflow to streams. This, in turn, leads to changes in streamflow and water quality. To find out more, go to our Manage Stormwater page, and take a look at the Non-point Education for Municipal Officials project - you don't need to be a municipal official to appreciate the wonderful fact sheets under "Publications."
Continue to the groundwater cycle. Use the next page and previous page buttons on the bottom of each page to read through all the pages.