NREM 407/507 WATERSHED MANAGEMENT Day 2

Transcription

1 NREM 407/507 WATERSHED MANAGEMENT Day 2 1. Review Hydrologic Cycle Terminology/Model 2. Summarize Differences Cropfield vs Perennial Watershed 3. Tues Lab Develop International River PPT bring flash drive & When The Rivers Run Dry 4. Group Quiz next Thursday Hydrologic Model/Terms

2 Team Effort - Apply The Following Terms to the Blank Hydrologic Model Start by labeling Sinks Atmospheric Sink (Storage) Rain, Snow Input Channel Canopy Surface Evaporation Channel Storage Plant Canopy Storage Stem flow Canopy Drip/Throughfall Surface/Depression Storage Sheet, rill, gully flow Surface runoff/overland flow Soil Water Storage Detention/Retention Storage Subsurface flow Subsurface Stormflow Water Table Groundwater Storage Groundwater flow Seepage Capillary Fringe Return flow Saturated Overland flow Bank Storage Storm flow Base flow Gaining stream Losing stream Suspended load Dissolved load Bed load Plant water uptake (Note where it comes from retention storage/capillary fringe) Plant storage Transpiration ET Liquid Watershed Output

3 Sinks/Sources Healthy Watershed Hydrologic Cycle Liquid Watershed Output

4 Atmospheric Sink (Storage) Lable Sinks/Sources Plant Storage Plant Canopy Storage Surface/Depression Storage Soil Water Storage Detention/Retention Groundwater Storage Stream Channel Storage Bank Storage Healthy Watershed Hydrologic Cycle Liquid Watershed Output

5 Atmospheric Sink (Storage) Sinks/Sources Pathways Plant Storage Plant Canopy Storage Surface/Depression Storage Soil Water Storage Detention/Retention Stream Channel Storage Bank Storage Groundwater Storage Healthy Watershed Hydrologic Cycle

6 ET Atmospheric Sink (Storage) Input (Rain, Snow, Condensation) Sinks/Sources Pathways WT Losing Stream Plant Storage Bed Load Plant Canopy Storage Suspended Load Surface Surface/Depression Storage Return flow Soil Water Storage Detention/Retention Capillary Fringe Water Table Sheet, rill Gully flow Groundwater Storage Seepage Subsurface Flow Subsurface Storm flow Stream Channel Storage Bank Storage Healthy Watershed Hydrologic Cycle Liquid Watershed Output Page 36 Reading Handout

7 Using terms from the hydrologic cycle develop a simple equation for Surface Runoff (SRO) In other words what has to happen to get surface runoff? SRO = Precip -

8 Answer. Using terms from the hydrologic cycle develop a simple equation for Surface Runoff (SRO) - SRO = Precip - Depression or surface storage -

9 Base flow Develop equations for: BF = Subsurface flow (SSF) + Storm flow SF = Channel (CI) +

10 Develop equations for: Answer. Base flow BF = Subsurface flow (SSF) + Groundwater flow (GF) Answer. Storm flow SF = Channel (CI) +Surface Runoff (SRO) + Return Flow (RF) + Saturated Overland flow (SOF) + Subsurface Stormflow (SSSF) SF = CI + SRO + RF + SOF + SSSF

11 Now Compare the Hydrologic Cycle between a natural ecosystem & an intensive crop system (worse-case scenario) annual summary

12 Water Movement In Disturbed & Undisturbed Watersheds Precipitation Crop Field Evapotranspiration Depression Storage Channel Stemflow Throughfall Surface Runoff Native Forest or Prairie Precipitation Evapotranspiration Stemflow Throughfall Stemflow Throughfall Water Table Unconfined Aquifer Surface Runoff Groundwater Plant Uptake Subsurface flow Confined Aquifer Surface Runoff Plant Uptake Groundwater Water Table

13 Parameter Is parameter greater or less in the Perennial Community than in the Crop Field? Depression Storage Channel Stemflow Throughfall Surface runoff Greater plant canopy and litter covering soil Less than cultivated ag field with low infiltration rates Less amount depends on size of stream & size of trees hanging over channel/small forested stream less interception; wider stream in cultivated area with more surface runoff, more channel interception More perennial woody plants & native grasses stay around even when tops are dead & plants are dormant Less more interception and canopy evaporation so less throughfall annually Vegetation and litter & no surface disturbance provides lots of macropores (good soil structure) for high infiltration More - because more water infiltrates into soil tillage could produce a plow pan at 6-8 inches that could restrict percolation & cause lateral movement near the soil surface Very little less than 1% in undisturbed natural forest and tall-grass prairie ecosystems because of high infiltration

14 Water Movement In Disturbed & Undisturbed Watersheds Precipitation Crop Field Evapotranspiration Sheet/Rill/Gully Erosion Native Forest or Prairie Plant Uptake & Storage Transpiration Evaporation Evapotranspiration Subsurface Flow Soil Macro & Micro Pores Precipitation Detention & Retention Storage Evapotranspiration Stemflow Throughfall Stemflow Throughfall Water Table Unconfined Aquifer Surface Runoff Groundwater Plant Uptake Subsurface flow Confined Aquifer Surface Runoff Plant Uptake Groundwater Water Table

15 Sheet/rill/gully flow Plant Uptake & Storage Transpiration Evaporation Evapotranspiration Subsurface flow Soil macro & micropores Detention & retention storage Very little high infiltration & lots of ground vegetation & litter - so very little surface runoff More perennial plants have longer growing season & larger & more diverse plant community corn & soybeans can take up a lot of water but only for a short time during the midsummer High perennial forest or prairie have high leaf area and deep root systems compared to corn and beans can transpire as much as 200,000 to 1,000,000 gal/ac/yr. Less soil shaded by trees and plants & covered by litter Lots more deep roots can pull water from whole vadose zone profile so the Tr is the big part of ET not E More more infiltration so more water in soil More macro less micro in surface soil because of lack of surface soil disturbance from cultivation or grazing More detention more macros but also a significant amount of retention because water gets into soil

16 Water Movement In Disturbed & Undisturbed Watersheds Crop Field Precipitation Soil Water Storage Antecedent Moisture Return Flow Saturated Overland Flow Subsurface Stormflow Peak Channel Discharge Water Table Depth Capillary Fringe Native Forest or Prairie Precipitation Evapotranspiration Evapotranspiration Stemflow Throughfall Stemflow Throughfall Water Table Unconfined Aquifer Surface Runoff Groundwater Plant Uptake Subsurface flow Confined Aquifer Surface Runoff Plant Uptake Groundwater Water Table

17 Soil water storage Antecedent moisture Return flow Saturated overland flow Subsurface storm flow Peak channel discharge Water table depth below surface Capillary Fringe Total more even with high evapo-transpiration because less than 1% runs off compared to 50-60% or more in the crop field Higher overall right after storm because more gets into soil & little evaporation but high transpiration may dry out later More because more gets into the soil with some chance of saturated conditions near the stream causing return flow More because more return flow & once a soil is saturated to the surface then there may be overland flow called saturated overland flow More more water into soil especially in area near the stream where the low areas may become saturated quickly Lower because of low surface runoff Nearer the surface because more gets into soil - when plants start transpiring lowers WT. In tiled landscapes crop fields WT will be low because of added drainage. Assuming all else the same more because more water in soil and higher water table macro/micro pore differences here are only based on texture and not cultivation because this is taking place too deep in the soil.

18 Water Movement In Disturbed & Undisturbed Watersheds Crop Field Shallow GW Storage Total Stormflow Baseflow Following Storm Dissolved & Suspended Load Bed Load Native Forest or Prairie Precipitation Precipitation Evapotranspiration Evapotranspiration Stemflow Throughfall Stemflow Throughfall Water Table Unconfined Aquifer Surface Runoff Groundwater Plant Uptake Subsurface flow Confined Aquifer Surface Runoff Plant Uptake Groundwater Water Table

19 Shallow groundwater storage Total Storm flow Base flow following storm Dissolved & suspended Bed Load More more water into soil A lot less very little surface runoff More because of low storm flow Less little surface runoff, storm flow so less less turbulent discharge which can cause erosion Less less erosion, less material in stream to be rolled, bounced along bottom Which scenario requires more stream channel storage?

20 An Example of What Happens When a Prairie Covered Watershed is Converted to Row Crop Agriculture