Calvert County’s watershed management planning is rooted in science-backed policy recommendations and addressed through our water monitoring programs.
Tidal water monitoring
The tidal program consists of summertime sampling of Mill Creek and eleven other tidal creeks: Hall, Hunting, Battle, Island, St. Leonard, Hellen’s, Hungerford, Fishing, Plum Point, Parker’s and Flag Harbor. These locations are measured for measured for water column temperature, salinity, dissolved oxygen, chlorophyll-a, and clarity.
Mill Creek is sampled across a total of ten stations, every two weeks between mid-May and mid-September. This dataset goes back to 1987.
Mill Creek continues to experience low dissolved oxygen levels. Bottom-water dissolved oxygen concentrations were slightly better in 2024 but there continues to be an apparent decline in long-term annual averages. The long-term annual average is 4.35 mg L-1, the 2024 average was 5.0 mg L-1. Hypoxia occurs when dissolved oxygen levels fall under 2.0 mg L-1—this is the threshold for harming marine life.
Eleven tidal creeks are sampled across a total of 32 stations, once a month between June and August. This dataset goes back to 2009, although some creeks were added as late as 2013. In 2024, the Upper Patuxent creeks had one instance of hypoxia at Battle Creek, and two instances were documented at Parkers Creek on the Western Shore.
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Read the full 2024 tidal water quality report or view the 2024 presentation. Data for the last few years are below but additional datasets may be requested from the Department of Planning & Zoning (please allow two weeks for processing).
The nontidal program involves quarterly sampling of twenty-seven nontidal waterways throughout Calvert County. Nontidal waterways were sampled quarterly between 2010 and 2018 for phosphate (PO4), nitrate+nitrite (NO23), ammonium (NH4), and total suspended solids (TSS). Read a synthesis report of this monitoring or view the 2021 presentation. This program is scheduled to restart in Winter of 2026, involving citizen scientists. If you’d like to learn more about participating in this program, please email Amalia.Pleake-Tamm@calvertcountymd.gov.
Drinking water
Drinking water is supplied to Calvert property owners either via a public water system or a privately owned well. Calvert’s Department of Public Works annually tests our drinking water quality; these reports are found on their drinking water quality reports page. Privately owned wells are the responsibility of property owners. Read a factsheet on maintenance or call the Calvert County Health Department at 410-535-3922.
The Patuxent Sentinel monitors conditions in Solomons including temperature, dissolved oxygen, pH, salinity, and sea nettle likelihood. The Univ. of Maryland, Chesapeake Biological Laboratory has been operating this program since 1938.
Bay Observation Boxes (BOBs) measure temperature, dissolved oxygen, pH, salinity, and electrical conductivity. This program is run by the Forrest Career and Technology Center.
DolphinWatch tracks bottlenose dolphin sightings in the Chesapeake Bay. The Univ. of Maryland, Chesapeake Biological Laboratory has been operating this program since 2017.