Overview
WHY WE NEED CLEAN WATER
Clean water is central to the health of the Cape’s natural ecosystems. Our coastal waters, estuaries and embayments support valuable shellfish such as oysters and clams, as well as important finfish such as winter flounder and striped bass. Waterbirds, migrating waterfowl, raptors and other wildlife feed on fish, shellfish and aquatic plants. Freshwater ponds and streams support numerous fish and wildlife species, including important diadromous species such as river herring and American eels, which live in both fresh water and the ocean. The Cape’s ecosystems and food webs depend upon clean water.
Clean water is also important for the Cape’s “blue economy,” where residents, visitors, and businesses rely heavily upon healthy aquatic ecosystems. Commercial and recreational fishing and shellfishing on Cape Cod, which provide millions of dollars in revenue each year, depend on the surrounding aquatic habitats to produce and sustain fish populations in abundance. In 2018, the economic value of Cape Cod’s commercial fisheries totaled over $73.6 million, accounting for over 11 percent of the economic value of the Commonwealth’s commercial fisheries (“Port by Port: Profiles and Analysis of the Massachusetts Commercial Fishery”). The economic benefits of high-quality water resources are also demonstrated by Cape’s strong tourism industry. In 2023, tourism contributed $2.7 billion to the local economy, supporting 14,100 tourism-related jobs (https://www.mass.gov/news/tourism-drives-economic-growth-in-massachusetts).
Finally, clean drinking water is critically important for human health. The water we drink comes from Cape Cod’s sole-source aquifer, a vast underground natural reservoir of groundwater. Federal, state and local laws are designed to protect a sole-source aquifer from pollution. However, as we discuss below, our groundwater, ponds, lakes, estuaries and embayments are all interconnected through the flow of water, meaning that pollution may spread among water resources depending on many factors.
WATERS OF THE CAPE
Cape Cod enjoys a wealth of water resources. These include saltwater and freshwater resources. Each major resource is summarized below. More information can be obtained at the Cape Cod Commission’s website on water resources.
Watershed: A watershed is an area of land where all the water that drains off it, or under it, goes to the same place (Cape Cod Commission, watersheds). Watersheds are the land areas that collect rain and snow, which drain into ponds, lakes, streams and groundwater, which in turn discharge into estuaries, embayments and the ocean. Nearly all of the Cape’s waters are connected by watersheds that collect water and discharge it into the ocean. Cape Cod has a total of 101 watersheds that discharge to the ocean. Of these, 53 discharge to embayments, which are susceptible to nitrogen pollution, and the remainder discharge directly to the ocean. Through the Section 208 Water Quality Management Plan for Cape Cod, the Cape Cod Commission has created a regional blueprint for protecting and improving water quality and tracking progress in implementation.
Groundwater: Groundwater is the lifeblood of the Cape. Rain and melting snow quickly soak into our sandy soils, where it collects to form a huge underground reservoir of groundwater that lies beneath most of the Cape. Water seeks the lowest elevation, so groundwater continues to move, seeking sea level, flowing into and out of ponds, feeding streams and flowing towards the coast, finding sea level when it enters our estuaries and embayments.
Groundwater is also the sole source of our drinking water. In 1982, the U.S. Environmental Protection Agency designated Cape Cod’s groundwater as a sole-source aquifer for drinking water under the federal Clean Water Act and Safe Drinking Water Act. All of the Cape’s drinking water comes from this sole-source aquifer, which is protected by local, regional, state and federal regulations. Nearly all of the Cape’s public water supplies are from groundwater wells; the one exception is Long Pond in Falmouth, which is itself groundwater-fed.
Freshwater ponds and lakes: Few people know that the Cape is the land of nearly a thousand lakes. At least 890 freshwater ponds and lakes cover nearly 11,000 acres, with individual ponds and lakes ranging in size from less than one acre to 735 acres, including 171 “great ponds” of 10 acres or greater in size (Cape Cod Commission, Ponds and Lakes). Because the Cape’s ponds and lakes are largely fed by groundwater, they are often referred to as “windows on our aquifer.” The sandy soils of the Cape allow groundwater to flow into and out of ponds. For this reason, pollution of ponds may also pollute groundwater and vice versa.
Hydrological cycle: The Cape receives about 45 inches per year of rain and melting snow. About 60 percent of this precipitation soaks into the ground to replenish groundwater. Most of the remaining 40 percent evaporates into the atmosphere where it provides moisture for storms that provide rain and snow (see below). A small amount becomes stormwater runoff. Due to the sandy soils, this runoff generally soaks into the sand and replenishes the aquifer. However, when runoff flows from roads, parking areas and fertilized lawns directly into wetlands, ponds or the ocean, pollutants from these developed areas can enter the water. Stormwater pollutants can include fertilizers, bacteria, soil particles, metals and de-icing compounds.
Groundwater is used up (depleted) when we withdraw it for drinking water and when it flows into ponds, streams, embayments and into the ocean. Ponds, streams and wetlands lose water due to evaporation, and trees also “breathe” water back into the air in a process called “evapotranspiration.” This evaporated water is not truly “lost.” Instead, it is critically important for feeding water back into the atmosphere to grow storms that produce rain and snow. Groundwater is replenished by rain and melting snow, which soak into the ground, beginning the hydrological cycle all over again.
WATER POLLUTION
Most of the Cape’s coastal embayments and many freshwater ponds and lakes are suffering from some form of pollution that originates from the land (i.e., stormwater), air (i.e., atmospheric deposition), groundwater, and/or surface water (including rivers, ponds, tidal embayments, etc.). Years of intensive studies and reports indicate that the Cape’s waters suffer from pollution due to the following pollutants and pollution sources.
Nutrient pollution: Excess nutrients (nitrogen and phosphorus) have caused severe eutrophication and severe ecological damage. Eutrophication refers to the harmful effects of excess nutrients on an aquatic ecosystem, resulting in increased growth of algae that leads to oxygen depletion. Oxygen depletion causes fish and shellfish kills and can impact other aquatic, terrestrial, and avian wildlife through a cascading effect in the food chain. Excess phytoplankton (microscopic algae) also causes water to become cloudy, reducing the amount of light in the water column, which impacts the growth of other beneficial aquatic plants such as eelgrass. In addition, when algae die, their remains settle to the bottom and decompose, causing more oxygen depletion and releasing nutrients back into the water, feeding the cycle of excess nutrients. Finally, the buildup of decaying organic matter on the bottom of ponds, lakes and embayments often results in thick, anoxic (low oxygen) muck that is unhealthy for shellfish, fish and other aquatic organisms.
Many of the Cape’s coastal embayments and estuaries are suffering from eutrophication caused by excess nitrogen, as demonstrated by the Massachusetts Estuaries Project and by the Section 208 Water Quality Management Plan for Cape Cod.
Ponds and lakes are also suffering from eutrophication caused by excess nutrients (Cape Cod Commission, Ponds and Lakes). While phosphorus has been targeted as the main cause of pond eutrophication, there is growing scientific evidence that nitrogen as well as phosphorus impacts the quality of freshwater ponds (Kniffin et al., 2009, Mischler et al., 2014, C. Neill, 2023).
On Cape Cod, excess nutrients originate largely from human sources and activities. The largest source of excess nitrogen and phosphorus is poorly treated wastewater (e.g., Title 5 septic systems) that discharge nutrients into groundwater. Figure 1 shows the areas on Cape Cod where wastewater leaches into the groundwater via Title 5 septic systems, based on information retrieved from the Cape Cod Commission in 2022. Another human activity that adds unwanted nutrients to water resources is the use of fertilizers on lawns, gardens, golf courses and farms; stormwater runoff then carries fertilizers into nearby ponds and streams. Some nitrogen also falls out from the atmosphere in precipitation; this atmospheric nitrogen largely originates from burning fossil fuels.
Figure 1. Map of areas served by Title 5 septic systems and publicly owned wastewater treatment facilities in 2022.
Harmful algal blooms and harmful cyanobacteria blooms include red tides in coastal waters and cyanobacteria blooms in freshwater ponds and lakes. In coastal waters, red tide is the common name for toxic phytoplankton that can form harmful algal blooms. Shellfish that ingest toxic phytoplankton can cause paralytic shellfish poisoning (PSP) in people who eat contaminated shellfish. The Massachusetts Division of Marine Fisheries (MA DMF) monitors coastal waters for harmful algal blooms and issues advisories and shellfish area closure notices as needed (MA DMF and red tide).
In freshwater, harmful cyanobacteria blooms thrive in nutrient-rich and warm waters. Cyanobacteria blooms are of concern because a number of common species produce toxins that can harm humans and animals if ingested (CDC, EPA). Since 2017, APCC’s Cyanobacteria Monitoring Program has documented cyanobacteria blooms in dozens of ponds throughout the Cape. APCC anticipates that this will be an increasing problem as nutrient pollution continues and the climate warms. APCC used cyanobacteria monitoring data and water quality data as two indicators of nutrient pollution for this report.
Harmful bacteria include bacteria that originate from fecal wastes (humans and/or animals). Examples of fecal bacteria are Escherichia coli (E. coli) and enteric bacteria. Fecal bacteria can cause illness in both humans and animals. On Cape Cod, most fecal bacteria contamination originates from domestic animals and wildlife. Failed septic systems (including flooded septic systems) are another source of bacteria. Bacteria are carried into water by stormwater runoff. State and federal water quality standards limit the amounts of fecal bacteria that can be present in waters where swimming and shellfishing are conducted. Swimming beach water quality is monitored by Barnstable County. The Massachusetts Division of Marine Fisheries monitors water quality in shellfish beds and limits shellfishing to waters that meet a stringent water quality standard for fecal bacteria.
Mercury pollution occurs in waters throughout the Northeast. As of November 2024, the Massachusetts Department of Public Health listed 30 ponds and lakes on Cape Cod with fish consumption advisories that warn people to limit or avoid eating fish from that lake due to mercury pollution (MA DPH Fish Consumption Advisories). Mercury pollution is caused by fallout of mercury from the atmosphere, a primary source of which originates from coal-burning fossil fuel plant emissions outside of Massachusetts. Incineration of medical wastes and municipal wastes also contribute mercury to the atmosphere. Our assessment does not address mercury pollution, but the State of the Waters: Cape Cod website provides information on mercury pollution and state fish consumption advisories for freshwater lakes and ponds on Cape Cod.
Emerging contaminants and pharmaceutical compounds have been found in groundwater and surface water throughout Cape Cod. This group of pollutants contains a wide variety of compounds, including endocrine-disrupting compounds, pharmaceutical drugs (including antibiotics), insect repellant, flame retardant, fluorinated compounds and PFAS (per- and polyfluoroacetate substances, see below). The Silent Spring Institute has been monitoring the Cape’s waters’ emerging contaminants. The Center for Coastal Studies and Silent Spring Institute also found pharmaceutical compounds in Cape Cod Bay and in groundwater near septic systems, pointing to septic systems as the source of these pharmaceutical compounds.
PFAS (per- and polyfluoroacetate substances) are manmade chemicals used widely in diverse items (e.g., fireproof clothing, non-stick pans, stain-and-waterproof fabrics, fire-fighting foam, dental floss, cleaning products, paints, electronics manufacturing and other industries and household products). PFAS compounds are also known as “forever chemicals” because they are long-lasting compounds. They have been found worldwide in humans, wildlife, water, soil and the air. PFAS have been found in Cape Cod water supplies, groundwater, and ponds. As of November 2024, nine ponds on Cape Cod had advisories due to PFAS (MA DPH Fish Consumption Advisories). PFAS compounds have been linked to human health impacts such as developmental disorders, immune system disorders, thyroid hormone disruption and cancer (CDC on PFAS). APCC’s PFAS Primer provides more information on PFAS. The six PFAS are: PFOS, PFOA, PFHxS, PFNA, PFHpA, and PFDA. MassDEP abbreviates this set of six PFAS as “PFAS6.” State regulations limiting PFAS6 in drinking water came into effect in 2021 and our drinking water grades address PFAS6.