Managing Streamflow: Low Flow and Flooding

Too much water leads to flooding, and too little water leads to low flow in our streams. Both extremes have a negative impact on our water quality and the wildlife that lives in our waterways. Heavy precipitation and periods of drought cannot be controlled, but NRWA does work to minimize human impacts on streamflow.

Low Flow

When precipitation is low and evapotranspiration reduces the amount of water in a stream, cool groundwater replenishes the stream and helps to sustain fish and other aquatic life through periods of drought-like conditions. However, other demands on groundwater can reduce the amount of water available to maintain healthy streamflow to rivers and streams. Water withdrawals from municipal drinking water wells, lawn watering, agriculture and other types of irrigation, and commercial and industrial uses reduce the water available. If the quantity of water withdrawn exceeds the amount of water replenished through precipitation and groundwater recharge, the result is a dry or low flow stream with decreased oxygen and raised water temperatures that stresses or kills fish and other aquatic life.

NRWA works to protect against the issues of low flow through projects that are in keeping with our Sustainable Water Use Policy, such as our Water Monitoring Program where volunteers track streamside conditions; through working with communities, state agencies and other environmental groups to encourage sustainable water policies; and through our education programs for adults on subjects such as Low Water Use Landscaping.

Flooding

In contrast to water withdrawals, impervious surfaces, such as asphalt roadways and parking lots, expanses of cement, and roof tops cause a rapid increase in flow to streams during heavy rainstorms or rapid snowmelts. This fast flow makes the streams rise quickly or be “flashy” and does not allow rainwater to infiltrate slowly back into the ground to replenish groundwater. Streams that receive water runoff quickly from impervious surfaces are prone to flooding, especially in urban areas. Rapid runoff not only causes flooding but also carries pollutants and sediment into our waterways, such as road oils, salt, sand, and yard chemicals.

NRWA works to protect against rapid runoff by helping developers and municipalities address the issue through good stormwater management and low impact development and other Smart Growth planning. The NRWA works with municipal Public Works personnel to discuss local stream quality and the impact of their road management practices. And we collaborate with Conservation Commissions, government agencies, and other organizations to protect wetland areas that serve as sponges absorbing large volumes of water during periods of excess precipitation. Our Purple Loosestrife Management Project is focused on helping to control this invasive species that threatens to take over natural wetlands ecosystems.

For more information on streamflow and NRWA water projects, please contact Martha Morgan, NRWA Water Programs Director, at (978) 448-0299, or email This email address is being protected from spambots. You need JavaScript enabled to view it..

Protecting Water Quantity: Streamflow and Sustainability

Throughout the world, water quantity issues are becoming more urgent, with some regions lacking sufficient water supplies and others dealing with an overabundance leading to flooding. Here in our watershed, streams and rivers are prone to both low flow and flooding.

The total amount of water in the rivers and streams of the Nashua River watershed is a function of the amount of precipitation, the amount of evapotranspiration (evaporation by trees and other vegetation), the amount of water that infiltrates to the groundwater, and the amount of water that is pumped for human consumption. Groundwater is interconnected with surface water in New England, and is an important component of streamflow, especially during the hottest, driest times of the year. Daily real-time streamflow data are available from five U.S. Geological Survey gages in the Nashua River watershed. Instantaneous flow values can be obtained from the gages, as well as historical data, back to 1935 at some locations. The National Weather Service also maintains an Advanced Hydrologic Prediction Service to predict precipitation and river cresting, especially during times of flooding.

The elements of nature impacting water quantity are beyond our control, but there are many human actions that also impact water quantity that can be dealt with through a good water management plan. The NRWA seeks an approach to water management that is sustainable for both human consumption and aquatic life, and has a Sustainable Water Use Policy in place to govern its decisions regarding sustainable water use. In accordance with that policy, our work seeks to address low flow and flooding, as well as river continuity, the impacts of dams and culverts on natural stream flow. We also collaborate with state officials, environmental organizations and advocacy groups to promote sustainable water policies for our watershed, and Massachusetts and New Hampshire at large.

For more information about water quantity issues and projects, please contact Martha Morgan, NRWA Water Programs Director, at (978) 448-0299, or email This email address is being protected from spambots. You need JavaScript enabled to view it..

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Working in Many Ways to Protect Water Quality

In addition to NRWA’s Water Monitoring Program and bacterial source tracking projects, we work on ecological river restoration, vernal pool certifications, and outreach and education about water-related issues. NRWA collaborates with Conservation Commissions and other local and state governing agencies regarding issues affecting rivers, streams, wetlands, lakes, and ponds. For instance, NRWA comments on surface water discharges, water withdrawals, dam removals, wetland filings, and Massachusetts Environmental Policy Act (MEPA) projects.

The following are examples of our other water protection projects:

• NRWA is a participant in the Wekepeke Watershed Restoration Initiative – a restoration effort in the “Clinton Water Works” region of the Wekepeke Brook sub-watershed in Sterling and Leominster. The Initiative stems from a study conducted by Rushing Rivers Institute. Restoration efforts will aim to improve native brook trout habitat in this important cold water fishery. More on the background of the Wekepeke study.
• NRWA met with Department of Public Works, Lions and Rotary Clubs, and Agricultural Commissions to increase awareness of good practices for road, lawn, field, and animal manure maintenance that help to keep our water clean.
• NRWA collected water samples on the Nashua River in Nashua, New Hampshire for a project undertaken by Essex Hydropower Associates to gather data on river conditions near the Jackson Falls dam.
• NRWA participates in regional projects like the Massachusetts Watershed Coalition’s Billion Gallons a Year (BGY) Initiative, the goal of which it to cleanse a billion gallons of stormwater in one year before it reaches local rivers and streams.

For more information about these or other water quality projects, please contact Martha Morgan, NRWA Water Programs Director, at (978) 448-0299, or email This email address is being protected from spambots. You need JavaScript enabled to view it..