The Water Quality Index is a combination of the Nitrogen, Phosphorus, Conductivity, and Turbidity indicators.
The Water Quality Index is a combination of the Nitrogen, Phosphorus, Conductivity, and Turbidity indicators.

The average of the Nitrogen, Phosphorus, Conductivity, and Turbidity indicator scores are used as one water quality indicator index.

For descriptions, measurement methods, and thresholds please refer to the individual indicator pages for watershed-focused information.

How is it scored?

The 2026 report card was the first year for which water quality watershed trends were calculated. Region scores were based on a 3-year rolling average ad a generalized linear model with log sample weight was used to calculate trends for the indicators and regions. The overall date range was from 1986–2024, but some regions had different start years based on data availability. The table below summarizes the ranges of years scored for each region:

RegionData time rangeYears of data
Chemung2004–202416
ChoptankInsufficient data5
ElizabethInsufficient data0
Juniata1986–202436
Lower Eastern Shore2000–202420
Lower James2004–202419
Lower Potomac2000–202425
Lower Susquehanna1986–202439
Lower Western ShoreInsufficient data6
Middle James1986–202431
Middle Potomac2000–202425
Middle Susquehanna1986–202439
Patapsco and Back2000–202412
PatuxentInsufficient data9
Rappahannock1988–202426
ShenandoahInsufficient data7
Upper Eastern Shore2000–202421
Upper James1999–202422
Upper Potomac1986–202427
Upper Susquehanna2004–202420
Upper Western Shore2000–202410
West Branch Susquehanna1986–202439
York1986–202432