Wetland Functions in the Watershed: Part 1 Watershed Elements. USDA NRCS Module Name 1

Transcription

1 Wetland Functions in the Watershed: Part 1 Watershed Elements USDA NRCS Module Name 1

2 Objectives Define Landscape Elements in the Watershed Describe Hydrologic Connections Between Elements Introduce Soil Hydrodynamic Concepts for Watersheds Introduce Spatial Techniques for Mapping Watershed Elements using GIS Define Functions by Landscape Elements USDA NRCS Module Name 2

3 Watershed Elements: Uplands Headwaters True Stream Reaches Active Channels Floodplain Landforms Watershed Network Map USDA NRCS Module Name 3

4 Uplands (Interfluves) Indiana Flatwoods Nebraska Sandhills Prairie Pothole Region Eastern Colorado USDA NRCS Module Name 4

5 Uplands - Watershed Network Interface Top pixel is 2.5 Acres in this example < 2.5 Acres is Upland Uplands Deliver water, sediment, etc. to watershed Reaches Shown 1-dimensionally USDA NRCS Module Name 5

6 Non Uplands shown 2-dimensionally with Soil Map Units USDA NRCS Module Name 6

7 Dry Uplands Sub-Humid and Drier Regions OR >2% Slopes Well Drained Drainage Class High Runoff OR High Recharge No soil saturation No ponding No flooding Kansas Flint Hills High Runoff (RCN) Low Recharge Dry Headwaters USDA NRCS Module Name 7

8 Dry Uplands Discharge Kansas Flint Hills Runoff Recharge Discharge These are Wetlands SLOPE HGM CLASS Even Dry Uplands With Low Recharge Create Wet Discharge Reaches USDA NRCS Module Name 8

9 Dry Uplands Upland Recharge Zone Nebraska Sandhills High Recharge Low Runoff (RCN) Wet Headwaters USDA NRCS Module Name 9 Headwater Discharge Zone

10 Wet Uplands Sub-Humid and Wetter Regions 0-2% Slopes Poorly Drained to Very Poorly Drained High Groundwater Table Some Ponding No Flooding Moderate to High Runoff Low to Moderate Deep Groundwater Recharge Medium to High Lateral Subsurface Flow USDA NRCS Module Name 10

11 Wet Uplands Much of U.S. Wet Uplands have been drained Drain outlets deliver dissolved nitrogen These are Wetlands MINERAL FLAT HGM CLASS USDA NRCS Module Name 11

12 Wet Upland Hydrology Lateral Discharge USDA NRCS Module Name 12

13 Headwaters Iowa Des Moines Lobe Utah Idaho Panhandle Nebraska Sandhills USDA NRCS Module Name 13

14 Headwaters Represent most of a typical watershed (reach length) Do not have distinct channels and floodplains Exist as wet gaining reaches or dry losing reaches Channel formation is a gully Upper boundary is lower boundary of upland Gullies are loss of Hydrologic Function not just erosion Headwaters are the 1 st Receiving landscape First concentration of surface runoff and/or groundwater discharge Nutrient Cycling Sediment Capture Water Storage USDA NRCS Module Name 14

15 Wet Headwaters Gaining Reaches Receive Groundwater Discharge Maintain D.S. Baseflows High Soil Organic Content, may even be Histosols Western Wyoming These are Wetlands SLOPE HGM CLASS Kansas Gyp Hills USDA NRCS Module Name 15

16 Wet Headwaters May be very large With large drainage areas Beaver Flow Western NY USDA NRCS Module Name 16

17 Gullied Wet Headwater Remnant Willows Lowered Groundwater Table Box Elder County, Utah USDA NRCS Module Name 17

18 Intact Wet Headwater - Upstream Reach USDA NRCS Module Name 18

19 Wet Headwater Hydrology Gi Groundwater Inflow Go Groundwater Outflow (Spring Flow) Ri Surface Runoff in Ro Surface Runoff Out USDA NRCS Module Name 19

20 Wet Headwater Water Hydrology Deep Discharge Shown Here Often is Shallow Subsurface Flow in Soil USDA NRCS Module Name 20

21 Wet Headwater Before Restoration Histosols Tussock Sedge Microtopography Near Continuous Surface Saturation Sequestered Carbon USDA NRCS Module Name 21

22 Wet Headwater After Restoration Lateral Effect Drawdown Mineralization and Subsidence USDA NRCS Module Name 22

23 Dry Headwaters Near Pinedale, Wyoming Kansas Grassed Waterway USDA NRCS Module Name 23

24 Dry Headwaters Receive Surface Runoff Provide Groundwater Recharge In the Reach from Watershed Runoff Functions: Recharge provides D.S. Baseflow Maintenance, too Transport Sediment Sandy Alluvial reaches have high recharge potential Reaches on fine textured soil, or rock have low recharge potential Degraded by: Channel formation or incision USDA NRCS Module Name 24

25 Dry Headwaters Can Still Store Water Recharge During Runoff Long Term Discharge Downstream Gully is Wet Q: What Happens to Downstream Baseflow? Upstream- Surface is Dry USDA NRCS Module Name 25

26 True Riverine Reaches - Otter Creek, VT Channel Backswamp Wetland Ponding Natural Levee +/- 3 Higher than Backswamp Non-Hydric USDA NRCS Module Name 26

27 Riverine Reaches Feature Geomorphic Channels Associated with Distinct Floodplains Formed and Maintained by Hydrograph Pulses Channel Maintained by High Frequency Sediment Transport Floodplain Maintained by Low Frequency Sediment Cycling Feature Unique Floodplain Landforms Natural Levees Splays Oxbows Scour Channels USDA NRCS Module Name 27

28 Franklin County, Kansas Blue Osage, Backswamp Red Verdigris, Natural Levee Web Soil Survey Ponding Frequency Map USDA NRCS Module Name 28

29 Compare Extent of Floodplain to Active Channel Bar Natural Levee Backswamp Upland Photo: US COE Regional Guidebook USDA NRCS Module Name 29

30 Floodplain Landforms are Ecological Sites Unique: Landform Plant Community Groundwater Table Flood Frequency Flood Duration Ponding Potential Soil USDA NRCS Module Name 30

31 Introducing - Endosaturated Riverine Tongue River, Wyoming Ninnescah River, Kansas Saturated from Below USDA NRCS Module Name 31

32 Endosaturated Riverine Features High Ksat Floodplains (Sands Gravels) Wet from high groundwater Attenuated hydrographs Strong Baseflow in channel Surface Flooding not needed to create wetland hydrology High groundwater No ponding Flooding need not be long duration or high frequency for ecological function Groundwater Rises and Falls with the Stream Water Surface USDA NRCS Module Name 32

33 Introducing - Episaturated Riverine Iowa photo: NRCS Photo Gallery USDA NRCS Module Name 33

34 Episaturated Riverine Features Low Ksat Floodplains (Silts and Clays) Weak Connection between stream water surface and floodplain Groundwater level Wet when inundated or ponded only Perched groundwater Ponding in backswamps Frequency and Duration of Flooding critical for ecological functions USDA NRCS Module Name 34

35 Episaturated Riverine Virginia USDA NRCS Module Name 35

36 In Both Cases The Hydrograph Drives the Function Hydroperiod USDA NRCS Module Name 36

37 End of Part 1 Questions? Wet Headwater Kansas Flint Hills photo: Jon Fripp USDA NRCS Module Name 37