Chapter 6

Soil and the Hydrologic Cycle

How does water move around on this planet?  97% of our world’s water is in the ocean our ground water only makes up another.7% our ground water only makes up another.7% of the.05% of the other water, 60% is in lakes and 33% trapped in the soil of the.05% of the other water, 60% is in lakes and 33% trapped in the soil

How does water move around on this planet?  Most of the clouds are therefore formed form the oceans by evaporation and transpiration together these two avenues of water into the atmosphere are called evapotranspiration (ET). This rain then falls on areas we call watersheds usually defined as river area bounded by mountains or hills that divide the waters movement from one another. This rain then falls on areas we call watersheds usually defined as river area bounded by mountains or hills that divide the waters movement from one another. We utilize the Tuolumne River watershed with Don Pedro the primary storage site with Modesto and Turlock reservoirs the secondary storage site. We utilize the Tuolumne River watershed with Don Pedro the primary storage site with Modesto and Turlock reservoirs the secondary storage site.

How does water move around on this planet?  Reducing ET and Evaporation Remove unwanted vegetation Remove unwanted vegetation Fallow periods for water replenishing Fallow periods for water replenishing Vegetative mulches and crop residues Vegetative mulches and crop residues Plastic mulches Plastic mulches ?? ??

How does water move around on this planet?  Water infiltration and percolation If water does not move into the soil, then run- off occurs If water does not move into the soil, then run- off occurs Water that is in the soil moves downward into least water potential area. Water that is in the soil moves downward into least water potential area. If the downward movement is impeded then the water backs up until it forms a lake or moves into another lower area.If the downward movement is impeded then the water backs up until it forms a lake or moves into another lower area. Drainage can reclaim high water saturated areasDrainage can reclaim high water saturated areas Surface draining – Ditches and slope Surface draining – Ditches and slope Sub-surface - Sub-surface -

Drainage  What do we do with our tail water?  What is the problem with tail water?

How does water move around on this planet?  Water infiltration and percolation (cont’d) Water and the dissolved elements move with the water to lowest areaWater and the dissolved elements move with the water to lowest area Applications for septic tanksApplications for septic tanks Enough percolation to have water move into the soil Enough percolation to have water move into the soil But not too fast as the soil cannot filter out the solids (150cm per hour) But not too fast as the soil cannot filter out the solids (150cm per hour)

How does water move around on this planet?  Irrigation methods Water is getting scarcer and more people want it we must use the present water in a more efficient manner. Water is getting scarcer and more people want it we must use the present water in a more efficient manner.

Irrigation  1. How do we measure water?  2. How do we decide what method to use? A. Climate A. Climate B. Type of crop B. Type of crop C. Cost of water (availability) C. Cost of water (availability) D. Slope of field D. Slope of field E. Physical properties of soil E. Physical properties of soil F. Drainage capability F. Drainage capability G. Salinity or other problems G. Salinity or other problems

Irrigation  1. Flood  2. Sprinkler  3. Drip

Flood - Types  1. Checks  2. Furrow A. Plastic or Alum. Pipes B. Gated Pipe C. Poly Pipe D. Permanent pipe (valves)

Sprinkler - Types  1. Hand Set  2. Permanent Set  3. Wheel Line  4. Center Pivot  5. Hose Drag

Drip - Types  1. Micro Emitters  2. In-Line Emitters  3. Adjustable Emitters  4. Drip Tape  5. Many more types

Soil Moisture Behavior  1. Saturation (1/10 Atmosphere)  2. Field Moisture Capacity (1/3 Atmosphere)  3. Permanent Wilting Percentage (15 Atmosphere)

How does water enter the soil?  through pores in the soil  sandy soils have the largest pores, but are often filled with other material  medium textured soils (loamy) have good water entry properties  clays, pores swell shut when they get wet

How does water move around on this planet?  Use of water for management of high salt soils Perhaps improved drainage to remove excess water Perhaps improved drainage to remove excess water Use more water to leach out the salts as long as there is a good clean source of water is available. Use more water to leach out the salts as long as there is a good clean source of water is available.

Salt movement in soil.