Setting the Course for Improve d Wa ter Qua litlity Hyygydrology in Watershed Systems Photo by Don Berger Minnesota Pollution Control Agency Session 5A: A TMDL traininggp prog ram f or local g overnment leaders and other water resource managers wq-iw3-55a Hydrology is one of many disciplines iildiTMDLtdinvolved in TMDL studies y cc l Agen o o Biology Contr ollution P P SilSocial Water sciences sota chemistry ee Minn In this presentation y cc BiBasic pri iilnciples o fhdlf hydrology l Agen oo Sources and pathways of flow in watersheds Contr Importance of hydrology to ollution TMDL studies and water PP quality management sota ee Minn Watersheds integrate physical, chilbililhemical, biological processes y cc A watershed is an area of land that drains to a common point l Agen oo TMDL s tu dies use watersheds as the Contr bioppyhysical basis for water quality planning and management ollution Watersheds integrate PP physical, chemical and biological sota ee processes Minn Minnesota Pollution Control Agency This module focuses on watershed hydrology What is “hydrology?” y cc “The study of water in l Agen oo all its forms (liquid, gas, and solid) on, in and over the land areas of Contr the earth” – Michigan DEQ ollution PP sota ee Hydrology is important at a global, regional or watershed scale Minn Hydrologic processes affect water quality y cc The movement of l Agen surface and oo groundwater results in the transport and Contr delivery of pollutants to waterbodies ollution PP sota ee Minn Minnesota Pollution Control Agency The hydrologic cycle hydrologic cycle c/o US EPA Why is hydrology important to TMDL s tu dies ? y cc Hydrology is critical to Before we can manage understanding the an impaired waterbody, l Agen sources and movement o o we must understand watershed hydrology of water (and pollutants) to a waterbody Contr Addressing water quality problems in water bodies will ollution require addressing hydrologic pathways P P (i.e. reducing surface runoff, increasing infiltration, etc.) sota ee Minn Sources of water affecting stfltream flow y cc Precipitation is the l Agen oo major source of new Each watershed also water in watersheds stores existing water Contr ollution PP sota ee Minn Types of precipitation contributing wattter to wa tersh hdeds y cc raifllinfall l Agen drizzle oo snow Contr sleet hail ollution P P fog sota ee dew frost Minn Precipitation affects the amount timing distribution quality of water moving through a watershed y cc Humans cannot control precipitation l Agen oo They can control land use decisions and human activities that can change Contr how much precipitation is intercepted and stored in watersheds ollution PP sota ee Minn Water storage and movement y A watershed is essentially cc an enormous precipitation collecting, storing and l Agen routing device oo Storage and movement of water within watersheds Contr ilinvolves a comp lex combination of many smaller processes ollution PP Infiltration and storage of precipitation minimizes sota ee surface runoff and reduce the movement of Minn pollutants to streams Water storage on earth can be natltural or man-made y cc any natural or man-made surface where Depression water collects and either seeps or l Agen storage evaporates (lakes, wetlands, ponds, oo reservoirs, etc.) Soil water water held within the soil Contr Vegetation used by plants ollution PP GdtGroundwater sattdturated zone (aqu if)ifers) Channel sota water held within the channel ee storage (stream, river, ditch) Minn – Adapted from Peter Block, 2002 Water movement in a watershed y cc The pathways for precipitation, l Agen from rainfall to stream flow, o o involves a combination of surface and sub-surface processes Contr Difficult to separate the various ollution P P pathways of flow sota ee Water can move between sources (source interactions) Minn Hyygpydrologic pathways in a watershed Evapotranspiration Precipitation Surface Channel runoff interception Infiltration & Water subsurface table flow Groundwater or base flow Channel storage (stream flow) Adapted from Kenneth Brooks, et. al., 2003 Ground water recharge and disc harge zones in wa ters he ds y cc the process of water soaking into the ground Recharge l Agen to replenish ground water aquifers oo a process by which subsurface water Discharge Contr becomes surface water ollution PP sota ee Minn Groundwater recharge zones within a wa ters he d y cc Recharge occurs in l Agen specific areas of a oo watershed Contr The nature and timing of ollution PP recharge depends on excessive water infiltration and sota ee percolation beyond plant roots Minn Minnesota Pollution Control Agency di h Groundwater recharge and sc h arge zones c/o USGS Groundwater discharge zones ithdin a watershed y Time needed for water to move from recharge cc zones to discharge points can be minutes to years l Agen oo Groundwater discharging to surface waters is mostly unseen, but if observed, is typically Contr seen as springs or seeps Groundwater discharges to surface waters can ollution PP greatly affect temperature, dissolved oxygen and other characteristics of water which can sota ee affect aquatic life Minn Drainage systems may impact the rechfharge of some deep aqu ifers y cc l Agen oo Subsurface tile drainage Contr lake ollution PP Deep aquifer sota ee Minn Minnesota Pollution Control Agency interactions in watersheds Surface / g roundwater Surface water / groundwater itinterac tions y Ground and cc surface water are often l Agen oo treated as separate Contr systems – however, they are ollution PP inextricably They should linked be studied as sota ee an integrated system Minn Surface water / groundwater itinterac tions y Pathways of the interaction cc are complex Interactions are neither l Agen oo constant, nor consilistently separate Contr Groundwater is the major source of base flow in ollution many Minnesota streams PP sota ee Minn Groundwater / surface water interactions can result in ga in ing or los ing s tream reac hes GainingGaining Gaining LosingLosing Losing stream reach stream reach WblWater table Water table Ground water Wetlands are an expression of ground- water andfd surface watitter interacti ons y cc l Agen oo Contr Photo: BWSR Photo: BWSR ollution PP sota ee Photo: NRCS Minn Wetlands with unusual groundtittidwater interactions y cc l Agen oo Contr c/o Scott County Bogs Fens ollution P P PerchedPhd water table Ground – water rich sota in calcium e e Regional water table carbonate Minn Summary y cc Hydrology concerns water in all its forms on, in and over the land areas of the earth l Agen oo The hydrologic cycle feeds flow in our streams, ultimately affecting water quality Contr WtWater s torage an d movemen tit invol ves a complex combination of many processes ollution PP sota ee Minn Summary y cc Specific areas within a watershed serve as recharge and discharge zones l Agen oo Surface water in lakes, streams and wetlands interacts with groundwater Contr BdtdihdlithBy understanding hydrologic pathways, we can influence water quantity and quality ollution PP sota ee Minn Now what? y cc Now we understand the importance of hydrology in watershed management. l Agen o o What do we do with that knowledge? Contr Use the following modules and worksheets to ollution P P hlhelp you scope and p lan your pro ject. sota ee Minn What’s next? y c c Future modules will address other disciplines related to watershed management: l Agen o o Biology Contr Water chemistry ollution P P sota ee (watershed assessment: land use, land cover, geography, soils, etc.) Minn Final thought y “A watch is compp,licated, but a cc watershed is complex. Remove one gear from the thousands in a watch l Agen oo and it , predictably , stops working. Pollute one river and the whole Contr watershed is likelyyg to shift and change in a thousand ways, but nobody can be quite sure if or when a toxic algal ollution bloom will appear in the lake. ” PP - Dr. Judith Van Houten sota University of Vermont ee Minn.