Maryland Biological Stream Survey

A Foundation of Sound Science to Ensure the Future of Maryland's Streams

The Maryland Biological Stream Survey (MBSS) was started by the Maryland Department of Natural Resources in 1993 as a pilot study in three watersheds. A second, larger demonstration project, expanded statewide, was conducted in 1994. The MBSS was Maryland's first probability-based or random design stream sampling program intended to provide unbiased estimates of stream conditions with known precision at various spatial scales ranging from large 6-digit river basins and medium-sized 8-digit watersheds to the entire state. The basis of the MBSS design is lattice or multi-stratification sampling that ensures all 1st through 3rd order (now 1st through 4th order), non-tidal streams in the sampling frame have a non-zero and known probability of being sampled. A stratified random design is a cost-effective way to characterize Maryland's 10,000+ miles of freshwater streams.

Current Status

From 2014 through 2018, MBSS conducted the fourth round of statewide random sampling. Round four analyses are underway. MBSS is currently in its fifth round of statewide random sampling. From 2021 through present, MBSS has also been sampling targeted areas around the state, as well as sites related to special circumstances, such as testing of protocol applicability in ephemeral and very small stream systems.


Goal and Objectives

The Maryland Biological Stream Survey's goal is to provide the best possible information for ensuring the protection and restoration of Maryland's stream ecological resources.​

Objectives to help meet this goal

  • Assess the current condition of ecological resources in Maryland's streams and rivers
  • Identify the impacts of acidic deposition, climate change, and other stressors on ecological resources in Maryland's streams and rivers
  • Provide an inventory of biodiversity in Maryland's streams
  • Assess the efficacy of stream restoration and conservation efforts to stream ecological resources
  • Continue to build a long-term database and document changes over time in Maryland's stream ecological condition and biodiversity status​
  • Communicate results to the scientific community, the public, and policy makers

Products and Applications of MBSS Data

MBSS data are used for countless studies about freshwater ecology. This section details some of the monitoring that Maryland DNR conducts that focus on certain issues in the State. Some include:

Reports and Publications

MBSS puts many of its reports, manuals, and fact sheets up on the web for public viewing. Included in this section are documents about the protocols used by MBSS. You can find many of these at the Publications page.

Map of Sites Sampled by MBSS

Every round of MBSS sampling includes a statewide survey of the watersheds in Maryland. Our interactive Stream Health map has information on sites sampled since 1995. The map may be used to learn more about the Maryland Biological Stream Survey, to receive an overview on the health of Maryland's waters, and check out a map that contains an incredible amount of data.​

Go there now.