Watershed Assessment and Diagnosis of Condition for August 20, 2007 Joe Magner and Greg Johnson MPCA

Participants’ Background Watershed management and/or hydrology coursework? Watershed and/or hydrology work experience? Stream geomorphology training and/or experience? MnDNR’s Healthy Rivers Water Course? Other?

Assessment of What? Condition of What? Water Quality Chemistry Biology Hydrology Habitat Land Use

MPCA Activities Point Source Pollution Water Quality Standards –Chemistry –Aquatic Life Support Nonpoint Source Pollution TMDLs – Total Maximum Daily Loads Impaired Waters

Watershed Systems Approach to TMDLs and Impaired Waters

A Watershed Approach Requires Understanding the “Whole ” Watersheds are complex systems where everything is connected –Begin by looking at the pieces, –But then make sure to integrate them in order to see “the whole” of what we are trying to manage

Definition of a Watershed “The total land area from which water drains to a particular stream, river, lake, or other point of interest” ©Kentucky Division of Waters

A watershed approach requires the integration of many different disciplines: Geology Soils Biology Geography Water Chemistry Hydrology Focus on hydrology basics today

-- Hydrologic cycle -- Sources and pathways of flow in watersheds -- Storage and movement of water in watershed Overview of Basic Hydrologic Principles:

Hydrology The occurrence, distribution, and movement of water both on and under the earth's surface

The Hydrologic Cycle Controls Water in the Environment

Sources of Water in a Watershed Precipitation Groundwater Storage (internal sources of water stored in lakes, wetlands, ponds, puddles, soil)

Kinds of Storage That Contribute to Watershed Hydrology Depression – any surface where water collects and either seeps or evaporates (lakes, wetlands, ponds, puddles) Channel – water held within the channel (stream, river) Soil Water– water held within soil profile Vegetation – used by plants Groundwater – saturated zone (aquifers)

Pathways for Water in a Watershed Various processes and pathways determine how much and how fast precipitation becomes stream flow The pathway from rainfall to stream flow involves a combination of surface and sub- surface flows Difficult to separate the various pathways of flow

of Flow in a Watershed Channel Interception Surface Runoff Infiltration and Subsurface Flow Rainfall Channel Storage (Stream Flow) Groundwater or base flow Adapted from Ken Brooks, 2003 Pathways ET Water table

Surface Water / Groundwater Interactions Ground and surface water are often treated as separate systems But, they are inextricably linked Pathways of interaction are complex

Groundwater Recharge and Discharge c/o USGS

Groundwater Recharge Recharge can occur in many portions of a watershed and over large areas Groundwater Discharge Areal extent and hydraulic characteristics govern amounts of recharge and discharge Groundwater is often the major source of base flow in streams Groundwater discharges typically seen as springs or seeps Groundwater discharges to surface waters can greatly affect temperature, dissolved oxygen and other characteristics of water which can affect aquatic life

Gaining and Losing Stream Reaches Water table Groundwater Water table Stream flow Gaining stream reach Losing stream reach While some stream reaches are fed by groundwater, other stream reaches feed aquifers

Summary Hydrology is the science concerned with the occurrence, distribution, and movement of water Hydrology is one part of a watershed systems approach A watershed approach involves integrating several scientific disciplines The actual pathway from rainfall to streamflow involves a combination of surface and sub- surface flows Water quantity and quality in an impaired waterbody can be influenced by managing hydrologic pathways

Why is hydrology important to TMDL Studies? To manage an impaired water, we must first understand the hydrology of the watershed Understanding hydrology is critical to understanding sources and pathways of pollutants to a waterbody Addressing water quality problems in waterbodies will often require managing hydrologic pathways

© Explore MN Tourism “Rivers and the inhabitants of the watery elements are made for wise people to contemplate and for fools to pass without consideration.” ---Izaak Walton