Advanced water quality analysis with GIS RESM 575 Spring 2010 Lecture 11

2 Today Part A Introduction to watershed analysis with GIS Part B Advanced water quality analysis Terrain analysis Lab 11a and 11b Basic hydro analysis tools Advanced watershed analysis with WCMS

Part A. Introduction to Watershed Analysis with GIS

4 Overview GIS significance Important datasets Concepts Analysis Tools

5 Why watershed analysis with GIS? Watershed analysis is a spatial issue Used to analyze regional stressors

6 Regional stressors 1. Stream sedimentation 2. Habitat loss 3. Forest fragmentation 4. Acid mine drainage 5. Acid rain 6. Flooding 7. Invasive and non- native species

7 Watershed based frameworks Integrative approach Legislative roots in the 1972 Clean Water Act Goal to clean up and protect US water bodies from point and nonpoint sources Designated uses – evaluated as part of the Clean Water Act

8 Watershed cataloging units USGS Regions (2 digit)USGS Sub-regions (4 digit) USGS Sub-basins (8 digit) USGS 8-Digit sub-basins in WV

9 Watersheds for WV NRCS 10 and 12 watersheds in WV (5 th and 6 th level) n=342 n=745

10 Issues More local watersheds needed One to one relationship between land cover runoff and receiving stream segment Track runoff from land to stream

11 Example of scale differences DNR Stocked streams Tier Reproducing trout streams Impaired streams Watershed boundaries

12 Solution Delineate watershed boundaries using the topography to guide us

13 Manual method

14 Subwatersheds

15 GIS and Water Resources GIS in watershed management: 1. Elevation surface is key 2. Delineate watersheds 3. Track flow from a point 4. Find intermittent stream paths 5. Calculate drainage areas Geographic information systems (GIS) is a valuable tool in water resources management

16 GIS use in the hydro cycle

17 Surface hydrology Determine where the water came from and where it is going Describe the behavior of water as it moves over the surface of the earth Analysis starts with the creation of a hydrologically correct surface (no sinks or peaks interrupting drainage direction) Include the entire drainage

18 Elevation surface or grid The starting point for all hydrological modeling in GIS USGS Digital elevation model 30m or 10m elevation cells, or 3m for WV Each cell or grid represents a value for the elevation

19 DEM sources for WV 30m (1972) found in the c:/gis-data06/grids/ directory as wv_elev Mosaic statewide 10m (1972) derived from 1:24,000 hypsography on the WVU Tech center website By 24K quad – partial state coverage 3m (2003) derived from 2003 SAMB photos on the WVU Tech Center website By 24k quad

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21 Helpful ArcGIS commands If you have a *.dem file To combine dems

22 3m to 30m DEM comparison

23 National 30m seamless DEMs

24 Other hydro products to note for WV Segment level watersheds 1:24K hydrology

25 Sinks Depressions in the DEM where water gets trapped A sink prohibits calculating future flow direction grid values. A sink occurs when all neighboring cells are higher than the processing cell. Sometimes they are natural features!

26 Flow direction Created from an elevation surface Direction values are assigned Flow direction grids are used in many hydro GIS functions Flow direction map

27 Flow direction Created from an elevation surface Direction values are assigned Flow direction grids are used in the other flow functions Flow direction map

28 Flow accumulation The accumulated flow is based upon the number of cells flowing into each cell in the output grid. The current processing cell is not considered in this accumulation. Output cells with a high flow accumulation are areas of concentrated flow and may be used to identify stream channels. Output cells with a flow accumulation of zero are local topographic highs and may be used to identify ridges

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30 Summary of spatial techniques and tools available within a GIS Elevation grid Flow direction Fill sinks Allows for additional landscape based analysis Flow accumulation Any sinks? Yes No Watersheds Stream delineations Riparian areas Stream order

31 Delineate watersheds Hydro toolbar in ArcGIS 9

32 Delineate watersheds interactively Interactive delineation for a point

33 Track flow from a point

34 Track flow from a point

35 Find intermittent stream paths Mapped streams from the 1:24,000 topomap

36 Find intermittent stream paths Mapped streams from the 1:24,000 topomap

37 Find intermittent stream paths Intermittent, debris slides, accumulators, path of easiest descent exist

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40 Find intermittent stream paths

41 5. Calculate drainage area Flow accumulation grid = tells us the number of cells of a certain area that flow to a point Drainage area?

42 5. Calculate drainage area Flow accumulation grid = tells us the number of cells of a certain area that flow to a point

43 Calculate drainage area So, if there are 280,721 cells that flow to that location… and each cell is 3m by 3m in size (9sq meters) Then The total drainage area is (280,721) * (9) = 2,526,489 sq meters Or 2,526,489 sq meters * = 624 acres

44 Summary points Watersheds are the key unit of analysis for examining water quality issues Scale issues require us to delineate smaller watersheds for local issues GIS can aid in watershed management by 1. Elevation grids 2. Delineate watersheds 3. Track flow from a point 4. Find intermittent stream paths 5. Calculate drainage areas

45 For basic hydrological modeling ArcGIS9 toolbar Lab 12 Hydrological Analysis Basics

Part B. Advanced Water Quality Analysis with GIS

47 Overview Terrain analysis concave/convexity, moisture index Finding potentially affected streams Expected mean concentration modeling WCMS (Watershed Characterization and Modeling System) ArcGIS 9 extension

48 Surface hydrology Rainfall - runoff relationships Runoff - above curve Losses - below curve interception depression storage evapotranspiration infiltration Rainfall Time Runoff Time

49 Runoff curve from gauge Source:

50 Watershed characteristics affecting runoff Watershed configuration size shape orientation stream network Topography Geology soils, infiltration and erosion characteristics Surface culture agricultural practices residential land use practices Structures hydrologic modification

51 Watershed Characteristics Affecting Runoff Watershed shape For a given area, watershed width affects the overland flow pattern Effects can be seen in terms of the time of concentration of flow The larger the width the longer the time of concentration

52 Possible Land-Water Transform Coefficients Water Land

53 Moisture index Simply a function of two factors: How much water is flowing into the area How fast the water can flow out Ln [(catchment area + 1) / (slope + 1)] NOTE: this is a relative moisture index, so the resulting numbers do not have units Higher more positive numbers are wetter Lower more negative numbers are drier

54 Calculating a moisture index Compute a flow accumulation grid Compute a slope grid Input into the raster calculator:

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56 Curvature

57 Curvature Areas of convex profile curvature = areas of erosion Areas of concave profile curvature = areas of deposition Convex surface Positive profile curvature Slope increasing Erosion Concave surface Negative profile curvature Slope decreasing Deposition

58 ArcMap Curvature tool Output profile curve raster dataset. This is the curvature of the surface in the direction of slope. This is the curvature of the surface perpendicular to the slope direction.

59 Curvature result convex concave

60 Identifying potentially affected streams Overland flow non point source pollution is the number one water quality problem in WV ( d List WVDEP) Almost 20% of the streams in WV are impaired and not meeting designated uses Sources include mine drainage, leaking or overflowing sewage systems, illegal homeowner discharges, runoff from agriculture and urban areas

61 Identifying potentially affected streams Source of potential pollution can be mapped as points (discharge seeps), lines (mining headwalls), or polygons (nonpoint source pollution) The source is used as the weight grid in the flow accumulation function A network streamgrid shows the stream and the location where the potential pollution would enter the stream

62 What we are trying to show – which streams and where in the streams runoff enters

63 Water quality estimation Mass balance approach A B C D E E = fn (A, B, C, D, E) Or E/flow = A/flow + B/flow + C/flow + D/flow

64 Expected mean concentration modeling EMC input is a land cover grid Aggregated classes and coefficients from literature (see refs at end) Total NitrogenTotal PhosphorousTotal Suspended Solids Urban Open/Brush Agriculture Woodland Barren Wetland NOTE: per acre loadings are aggregated to 30m pixels for mg/L concentrations

65 EMC Export Coefficients year to year changes in precipitation soil type slope and slope morphology (convex, concave) geology cropping practices timing of fertilizer application relative to precipitation events density of impervious surface Factors likely to vary across watersheds:

66 EMC modeling approach Nutrient export coefficients are multiplied by the amount (area) of a given land cover type Incorporates the location of the cover class in the downstream routing of the pollutant Used as simulations to estimate the probability of increased nutrient loads from land cover composition A screening approach due to assumptions

67 EMC modeling approach EMC grid Annual runoff grid Cumulative runoff grid Stream flow grid Pollutant output grid * /= = Annual runoff grid

68 Limitations with stream flow model lack of interception, evapotranspiraiton, baseflow from groundwater rate of areal distribution of rainfall monthly averages was crude Limited to natural systems (no dams or impoundments)

69 Limitations with EMC approach year to year changes in precipitation soil type slope and slope morphology (convex, concave) geology cropping practices timing of fertilizer application relative to precipitation events density of impervious surface

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71 WCMS ArcGIS 9 extension

72 Further reading Jenson S. K. and J. O. Domingue Extracting Topographic Structure from Digital Elevation Data for Geographic Information Systems Analysis, Photogrametric Engineering and Remote Sensing. Vol. 54, No. 11, November 1988, pp Haith A. D and L.L Shoemaker Generalized Watershed Loading Functions for Stream Flow Nutrients. Water Resources Bulletin, American Water Resources Association, Vol 23, No. 3. Pp 471 – 477. Mark, D. M ‘Network Models in Geomorphology’, Modeling in Geomorphological Systems. John Wiley. Olivera, F., R. J. Chareneau and D. R. Maidment CRWR Online Report 96-4: Spatially Distributed Modeling of Storm Runoff and Non-Point Source Pollution Using GIS. Saunders, W. K. and D. R. Maidment (1996), A GIS Assessment of Nonpoint Pollution in the San Antonio-Nueces Coastal Basin, Center for Research in Water Resources Online Report 96-1, University of Texas, Austin, TX. Saunders, W. K. (1999) Preparation of DEMS for use in Environmental Modeling Analysis, In: Conference Proceedings: 1999 ESRI User Conference, Environmental Systems Research Institute, Redlands, CA. Shreve, R. L Statistical Law of Stream Number, Journal of Geology. Vol. 74, pp Strahler, A. N Quanitative Analysis of Watershed Geomorphology. Transactions of the American Geophysical Union. Vol. 8, Number 6, pp Tarboton, D. G., R. L. Bras, I. Rodriquez-Iturbe On the Extraction of Channel Networks from Digital Elevation Data, Hydrological Processes. Vol. 5, pp Reed, S.M., and D.R. Maidment CRWR Online Report 95-3: A GIS Procedure for Merging NEXRAD Precipitation Data and Digital Elevation Models to Determine Rainfall-Runoff Modeling Parameters.