RACC High School Training June 26, 2012 Jody Stryker University of Vermont Introduction to Watershed Hydrology

What is a watershed? An area of land that drains water, sediment, and dissolved materials to a common outlet. Watershed are separated by drainage divides. Can be any shape and size. Sub-watershed = watershed within a watershed. “Watershed” = “catchment” = “drainage basin” Elevation LEGEND flow lines sub-watersheds

Within a watershed Image credit: Watershed Activities to Encourage Restoration,

What happens downstream? Figures show dead zone near mouth of Mississippi River, Gulf of Mexico. Image credit: APA News/NASA Image credit: NOAA

Stream order Headwaters Confluences Image Credit: Developed by T. Endreny at SUNY ESF in the Department of Environmental Resources EngineeringT. EndrenySUNY ESFDepartment of Environmental Resources Engineering Outlet

Global hydrologic cycle Figure credit: URI Water Quality Home

Rainfall to runoff Precipitation Interception by canopy Transpiration Infiltration Root uptake Overland runoff Evaporation Stem-flow Subsurface flow Infiltration Groundwater flow Subsurface flow (interflow) Overland flow

Runoff pathways Source: M. Ritter, The Physical Environment. Groundwater flow Subsurface flow (interflow) Overland flow

Source: M. Ritter, The Physical Environment. Surface runoff is affected by... Climate characteristics such as: Type of precipitation Rainfall intensity Rainfall duration Rainfall distribution Antecedent precipitation and soil moisture...

Surface runoff is affected by... Physical characteristics such as: Land use Vegetation Soil Basin shape Elevation Slope Topography Drainage patterns... Source: M. Ritter, The Physical Environment.

V-shaped valley of a humid, temperate landscape Photo credit: Field Studies Council, UK Badland topography of an arid landscape Photo credit: National Park Service … landforms reflect dominant runoff processes

Effects of development on runoff Image credit: Minnesota Center fro Environmental Advocacy

Effects of development on runoff Image credit: Minnesota Center fro Environmental Advocacy Natural Landscape Low runoff High infiltration and recharge Healthy summer stream flow Natural pollutant treatment Developed - High runoff, low recharge - Lower water tables - Low stream flow -Nuisance flooding

Measuring river runoff Steps: 1.Measure stream stage (height of water surface). 2.Measure discharge. 3.Define relationship between stage and discharge. Image credit: Vermont EPSCoR CWDD,

Measuring river runoff Steps: 1.Measure stream stage (height of water surface). Diagram of a typical USGS stream gage with stilling well. Image credit: The USGS Water Science School,

Measuring river runoff Steps: 2.Measure discharge. Discharge = velocity * width * depth Image credit: The USGS Water Science School,

Measuring river runoff Steps: 3.Define relationship between stage and discharge. Image credit: The USGS Water Science School,

Hydrograph A way to look at the response of a watershed to hydrologic event Discharge (cms/cfs) vs. time Comprised of base flow and direct flow

Hydrograph pattern is the result of: Image credit: BBC: Intermediate Geography Rivers Watershed characteristics

Hydrograph pattern is the result of: Climate Humid vs. arid Previous rainfall Storm characteristics Intensity Duration Spatial distribution of events Image credit:

Image credit: Battle River Watershed Alliance, CA.

Stream channel morphology Image credit: Fisheries and Oceans Canada,

Stream morphology and stream health Image credit: Vermont Water Quality Division

Climate change and hydrology What climate related changes might we see?

Climate change and hydrology What climate related changes might we see? – Higher surface temperatures – Reduced snowpack – Increased drought conditions – Increase in regional precipitation – Longer growing seasons – Greater frequency of extreme events

Climate change and hydrology What hydrologic changes might we see? What climate related changes might we see? – Higher surface temperatures – Reduced snowpack – Increased drought conditions – Increase in regional precipitation – Greater frequency of extreme events

Climate change and hydrology What hydrologic changes might we see? – Higher runoff – More erosion – Increased transportation of dissolved materials – Increased flooding frequency and/or magnitude – Geomorphic channel adjustments – More altered landscapes – Higher water demand What climate related changes might we see? – Higher surface temperatures – Reduced snowpack – Increased drought conditions – Increase in regional precipitation – Greater frequency of extreme events

Climate change, hydrology, new challenges Image credit: Vermont Agency for Natural Resources Image credit: Vermont Watershed Management Division

Hydrologic effects of deforestation/development Image credit: USGS,

An experiment Sprinkle rainfall on “forested” watershed – collect runoff in cup Deforest and develop your watershed Sprinkle rainfall on “developed” watershed – collect runoff in cup

An experiment In each case consider: How much of rainfall runs off? How long before runoff begins at the bottom of the watershed? What happens when rainfall stops?

how much Influences how much water runs off how and where Influences how and where water runs off Why does land use matter?