Setting the Course for I d W t Q litImproved Water Quality

Hydrology in y gyWatershed SystemsSystems

Photo by Don Berger Minnesota Pollution Control AgencySession 5A: A TMDL training program for local government leaders g p g f g

and other water resource managers wq-iw3-55a

Hydrology is one of many disciplines i l d i TMDL t di

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involved in TMDL studies

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S i l

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sciencesWater chemistry

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In this presentationcy

In this presentation

B i i i l f h d l

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Sources and pathways of

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Importance of hydrology to TMDL studies and water

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Watersheds integrate physical, h i l bi l i l

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chemical, biological processes

A watershed is an area

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of land that drains to a common pointTMDL t di

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tro TMDL studies use watersheds as the biophysical basis for

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p ywater quality planning and managementWatersheds integrate

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physical, chemical and biologicalprocesses

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This module

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What is “hydrology?”cy

What is hydrology?ol

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“The study of water in all its forms (liquid gas

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all its forms (liquid, gas, and solid) on, in and

over the land areas of

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n the earth” – Michigan DEQ

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Hydrology is important at a global regional or watershed scale

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ne Hydrology is important at a global, regional or watershed scale

Hydrologic processes affect water lit

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quality

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The movement of surface and

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delivery of pollutants

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The hydrologic cyclecy

The hydrologic cycle ol

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c/o US EPA

Why is hydrology important to TMDL t di ?

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TMDL studies?

Hydrology is critical to

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an impaired waterbody, we must understand

Hydrology is critical to understanding the sources and movement

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to a waterbody

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Addressing water quality problems in water bodies will require addressing hydrologic pathways

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(i.e. reducing surface runoff, increasing infiltration, etc.)

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Sources of water affecting t fl

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stream flow

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Precipitation is the major source of new Each watershed also

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major source of new water in watersheds

Each watershed also stores existing water

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Types of precipitation contributing t t t h d

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water to watersheds

i f ll

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drizzle

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frost

Precipitation affects the amountamount timing distribution

litquality of water moving through a watershed

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tro They can control land use decisions and human activities that can change how much precipitation is

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n how much precipitation is intercepted and stored in watersheds

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Water storage and t

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movementA watershed is essentially

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yan enormous precipitation collecting, storing and routing device

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Storage and movement of water within watersheds i l l

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n involves a complex combination of many smaller processes

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Infiltration and storage of precipitation minimizes surface runoff and reduce

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Water storage on earth can be t l d

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natural or man-made

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Depression storage

any natural or man-made surface where water collects and either seeps or evaporates (lakes wetlands ponds

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storage evaporates (lakes, wetlands, ponds, reservoirs, etc.)

Soil water water held within the soil

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Vegetation used by plants

G d t t t d ( if )

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Channel storage

water held within the channel (stream river ditch)

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– Adapted from Peter Block, 2002

Water movement in a watershedcy

Water movement in a watershedol

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Difficult to separate the various pathways of flow

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Water can move between sources

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Hydrologic pathways in a watershedy g p y

PrecipitationEvapotranspiration

ChannelSurface

ff Channel interception

runoff

Infiltration &subsurface Water

flow

Groundwater or base flow

table

Channel storage(stream flow)

or base flow

Adapted from Kenneth Brooks, et. al., 2003

Ground water recharge and di h i t h d

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discharge zones in watersheds

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Recharge the process of water soaking into the ground to replenish ground water aquifers

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Discharge a process by which subsurface water becomes surface water

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n becomes surface water

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Groundwater recharge zones ithi t h d

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within a watershed

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specific areas of a

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pwatershed

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The nature and timing of

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excessive water infiltration and percolation beyond plant roots

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Groundwater recharge and di h

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discharge zones

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c/o USGS

Groundwater discharge zones i t h d

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in a watershedTime needed for water to move from recharge

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gzones to discharge points can be minutes to years

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tro Groundwater discharging to surface waters is mostly unseen, but if observed, is typically seen as springs or seeps

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n seen as springs or seeps

Groundwater discharges to surface waters can greatly affect temperature dissolved oxygen

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and other characteristics of water which can affect aquatic life

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Drainage systems may impact the h f d if

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recharge of some deep aquifers

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Subsurface tile drainage

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lake

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Deep aquifer

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Surface / groundwater

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ginteractions in watersheds

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Surface water / groundwater i t ti

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interactionsGround and

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are often treated as

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tro treated as separate

systems –

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inextricably They should

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They should be studied as an integrated

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Surface water / groundwater i t ti

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interactionsPathways of the interaction

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yare complexInteractions are neither

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tro constant, nor consistently separateGroundwater is the major

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n Groundwater is the major source of base flow in many Minnesota streams

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Groundwater / surface water interactions can lt i i i l i t hresult in gaining or losing stream reaches

GainingGaining LosingLosingGaining Gaining stream reachstream reach

Losing Losing stream reachstream reach

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Water tableGro nd ater

Water table

Groundwater

Wetlands are an expression of ground-t d f t i t ti

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water and surface water interactions

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Photo: BWSR Photo: BWSR

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Photo: NRCS

Wetlands with unusual d t i t ti

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groundwater interactions

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c/o

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Bogs Fens

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Ground –water rich in calcium

Perched water table

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Summarycy

Summary

Hydrology concerns water in all its forms on, in

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Hydrology concerns water in all its forms on, in and over the land areas of the earth

The hydrologic cycle feeds flow in our streams

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tro The hydrologic cycle feeds flow in our streams, ultimately affecting water quality

W t t d t i l

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n Water storage and movement involves a complex combination of many processes

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Summarycy

Summary

Specific areas within a watershed serve as

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Specific areas within a watershed serve as recharge and discharge zones

Surface water in lakes streams and wetlands

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B d t di h d l i th

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n By understanding hydrologic pathways, we can influence water quantity and quality

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Now what?cy

Now what?ol

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nc Now we understand the importance of hydrology in watershed management.

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What do we do with that knowledge?

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Use the following modules and worksheets to h l d l j

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What’s next?cy

What s next?

Future modules will address other disciplines

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Future modules will address other disciplines related to watershed management:

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Biology

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Water chemistry

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(watershed assessment: land use, land cover, geography, soils, etc.)

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Final thoughtcy

Final thought

“A watch is complicated, but a

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p ,watershed is complex. Remove one gear from the thousands in a watch

and it predictably stops working

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and it, predictably, stops working. Pollute one river and the whole

watershed is likely to shift and change

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n y gin a thousand ways, but nobody can be quite sure if or when a toxic algal

bloom will appear in the lake ”

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- Dr. Judith Van HoutenUniversity of Vermont

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