WETLANDS

1. WETLANDS • Predominance of hydric soils • Support hydric vegetation • Usually have ponded water at least 1 to 2 weeks during the growing season

2. NRCS Definition of Wetlands • Inundated for 7 days or saturated for 14 days during the growing season at least once every 2 years. • Inundation means standing water on the surface. • Saturated means wet surface by capillary action.

3. NRCS Definition of Wetlands • Growing season means between last 28oF in Spring and first 28oF in the Fall. • Each segment must be at least one-half acre in size.

4. Benefits of Wetlands • A unique wildlife habitat • Support water based recreational activities • Natural downstream flood control • Natural treatment and filtering system for polluted water • Potential source of ground water recharge

5. How Wetlands Affect Water Quality • Filter out sediment and suspended solids • Adsorb Chemicals on Organic Matter • Absorb Nutrients into Living Plant Tissue • Anaerobic Conditions Promote Denitrification • Increased Residence Time for Degradation of Pesticides

6. Factors Affecting Wetland Water Quality Treatment • Hydroperiod: The number of days per year that surface water is present. • Water Regime: the Frequency, Duration, and Depth of Flooding • Soil-Root-Water Interfaces • Vegetation Types

7. Wetland Vegetation • Different Species Prefer Different Environments • Hydrologic • Nutrient • Substrate Conditions

8. Desirable Vegetation Traits for Water Treatment • Rapid Growth Rate • High Tissue Nutrient Content • Production of large amounts of biomass.

9. Loading Factors Affecting Wetland Water Quality • Hydraulic Loading: ac-in/ac/day • 4 • BOD5 and TSS Loadings: lb/ac/day • 82 • Total Nitrogen: lb/ac/day • 3 • Retention Time in days • 5

10. PROBLEMS ASSOCIATED WITH WETLANDS • Few economically beneficial crops grow well on wetlands, including forests • Impediment to land forms of transportation • Most human structures must be built on dry land , including roads • Breeding ground for mosquitoes • Potential increase in downstream flooding

11. WETLAND RESTORATION

12. WETLAND RESTORATION

13. Definition of Drainage • The management of excess water on the land or in the soil • Cropland • Recreation Areas • Building Foundations • Roadways

14. Problems Caused by Excess Surface Moisture • Impede Surface Traffic • Encourage Mosquitoes • Contribute to excess subsurface moisture

15. Problems Caused by Excess Subsurface Moisture • Reduced soil aeration • Formation of toxic compounds • Reduced root respiration and growth

16. Problems Caused by Excess Subsurface Moisture • Reduced soil strength • Reduced load carrying capacity • Increased soil compaction from traffic

17. Problems Caused by Excess Subsurface Moisture • Increased Soil Specific Heat • Soil stays cooler longer in the spring • Delay the start of the growing season

18. Problems Caused by Excess Subsurface Moisture • Reduced Water Infiltration • Increased Surface Runoff • Increased Soil Erosion

19. Benefits of Drainage of Cropland • Improved trafficability • Increased length of the growing season • More efficient use of soil moisture • More efficient use of soil nutrients • More efficient use of land resources

20. Classification of Agricultural Drainage Systems • Surface • Subsurface • Interceptor • Relief

21. DRAINAGE HYDROLOGIC CYCLE EVAPOTRANS -PIRATION PRECIPITATION SURFACE INFLOW SURFACE RUNOFF SURFACE DEPRESSION STORAGE SUBSURFACE OUTFLOW SUBSURFACE INFLOW INFILTRATION SOIL MOISTURE STORAGE AST324\TEXT\DRAINAGE.PPT

22. Methods to Improve Land Drainage • Reduce surface inflow • Improve surface drainage • Reduce subsurface inflow • Improve subsurface drainage

23. Drainage Capacity Peak Inflow Rate FLOW RATE volume time Average Flow Rate TIME

24. VOIDS SOLIDS SOIL-WATER-AIR • Soil is made up of solids and voids • Voids in dry soil are filled with air • Voids in saturated soil are filled with water • Most roots require at least 10% air by volume • Only subsurface drains can increase soil air volume.

25. SURFACE DRAINAGE • Are not very effective at improving soil aeration • Use where soils are too tight for subsurface drains to work • Use where outlets are too shallow for subsurface drains to work

26. Benefits of Surface Drainage • Improve Surface Conditions for Field Travel • Reduce Mosquito Problems • Reduce Infiltration into poorly drained soils

27. Effects of Surface Drainage on Water Quality • Surface Drains reduce infiltration and increase surface runoff • Improving surface drainage reduces the residence time of chemicals on the field • Improving surface drainage only may result in increased losses of pesticides

28. Effects of Surface Drainage on Water Quality • Improving surface drainage only usually results in increased losses of sediment • Improving surface drainage only usually results in increased losses of phosphorus

29. SUBSURFACE DRAINAGE • Remove gravitational or free water • Increase the volume of soil from which roots can obtain nutrients • Increase the movement and quantity of air in the soil

30. BENEFITS OF SUBSURFACE DRAINAGE • Providing conditions that permit the soil to warm up faster in the spring • Increased soil bacterial activity • Reduced soil erosion • Removing toxic substances from the root zone

31. WATER QUALITY IMPACTS OF SUBSURFACE DRAINAGE • Reduced loss of sediment • Reduced loss of organic matter • Reduced loss of potassium and phosphorous • Increased loss of nitrate-nitrogen • Increased loss of soluble salts • May cause streams to dry up during prolonged dry weather

32. MOVEMENT OF WATER INTO SUBSURFACE DRAINS Water Table

33. MOVEMENT OF WATER INTO SUBSURFACE DRAINS Water Table

34. MOVEMENT OF WATER INTO SUBSURFACE DRAINS

35. OUTLETS: • natural streams, watercourses, or lakes • constructed drainage ditches • drain sump with pump outlet

36. OUTLETS: • The water should be able to drain away freely. • Provide protection from erosion • Provide protection from damage by livestock, floating ice, freezing and thawing. • Prevent entry of burrowing animals • May need flood gate on larger streams

37. DEPTH OF SUBSURFACE DRAINS • Minimum of 2 feet • Never below the impervious layer unless needed to get minimum depth • Depths greater than 6 feet are more expensive • Increased depth will allow wider spacing

38. SPACING OF SUBSURFACE DRAINS • Tight soils require closer spacing. • Closer spacing will allow faster removal of water • Wider spacing will reduce the cost of installation

39. GRADES ON SUBSURFACE DRAIN LINES • Too flat a grade will require larger pipe diameter for the same performance, and may cause problems with sediment accumulation in lines • Seldom use S < 0.1% • Steep grade will cause erosion and blowout problems

40. DRAINAGE RATES: • Most designs use a Drainage Coefficient defined as a depth of water to be removed from the area in one day (24 hours) • Depend on the type of soil, the type of crop, and the degree of surface drainage.

41. Drainage CoefficientsTable 13.2 in the Text • Field Crops with Normal Surface Drainage on Mineral Soils • 3/8 to 1/2 inch per day • Field Crops with Surface Inlets on Mineral Soils • 1/2 to 1 inch per day

42. Drain Capacity • A = 100 acres • Dc = 1/2 inch/24 hours

43. Drain Pipe DiameterEq. 13.2, page 242 in Text

44. Pipe Diameter Example • Q = 2.08 CFS • S = 0.1% =0.001 • Corrugated Plastic Tubing, n = 0.015

45. Pipe Diameter Example Use the Next Largest Size