Precipitation and climate • Soil moisture/type • Impervious cover (roads and buildings) • Groundwater storage • Riparian Areas (rivers and streams) What does water availability depend on?
Groundwater – farmers can draw water directly from groundwater reservoirs to use with any irrigation technique, but this depends on aquifers being replenished in accordance with their water needs • Nearby rivers or streams (surface water)– Irrigation canals can be dug to divert or connect close-by rivers or stream onto fields. Aqueducts can transport water aboveground to croplands. Pumps near river can pull water through underground pipes to fields to be used for any irrigation method. Where to Get the Water?
the controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall. What is irrigation?
Evapotranspiration - amount of water transpired & utilized by the crop + evaporation from the soil • Some crops require 500 lbs of water to make 1 pound of dry matter • This water can come from stored water in the soil, supplied by rain, groundwater within reach of the roots, or from irrigation What is Evapotranspiration?
1) Furrow/Flood irrigation: submerge entire surface of land with water. • 2) Sprinkler: spray from above using mechanized sprinkler systems. • 3) Drip irrigation: apply water directly to roots with applicators under ground What are some types of irrigation?
Leveling of fields - using leveling equipment, some of which is guided by a laser beam, to scrape a field flat before planting. That allows water to flow evenly throughout the fields. • Surge flooding - Traditional flooding involved just releasing water onto a field. In using surge flooding, water is released at prearranged intervals, which reduces unwanted runoff. • Capture and reuse of runoff - A large amount of flood-irrigation water is wasted because it runs off the edges and back of the fields. Farmers can capture the runoff in ponds and pump it back up to the front of the field where it is reused for the next cycle of irrigation. 50-80% Efficient Furrow/Flood Irrigation
55-75% Efficient • Needs electricity • A lot of water evaporates before reaching crops Sprinkler Irrigation – Center Pivot
55-75% Efficient • Produces much less even irrigation than center pivots • Needs electricity • A lot of water evaporates before reaching crops Sprinkler Irrigation – Moveable Risers
80-95% Efficient • Water is sent through plastic pipes (with holes in them) that are either laid along the rows of crops or even buried along their rootlines. Evaporation is cut way down, and up to one-fourth of the water used is saved, as compared to flood irrigation. Drip Irrigation
Pros and Cons of Drip Irrigation PROS Efficient use of water Applied evenly ensuring a balanced distribution of nutrients and salts. Reduced nutrient and chemical leaching Less waste of water and runoff into stream. Cost-effective CONS Costly investment Requires frequent maintenance Requires constant monitoring Water requires quality management, including cleaning through filtration to prevent clogging the outlet valves Troubleshooting drip irrigation can be difficult.
Mulch – reduces water needs Protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mimics the leaf cover that is found on forest floors. Can be made of leaves, hay, straw, cocoa hulls, compost, recycled tire rubber, etc.
What causes loss of recharge areas? • Roads, sidewalks and roofs channel their run-off into surface water increasing flows of streams, and decreasing ground water recharge.
Groundwater Storage (or Loss)? • Wetlands absorb large amounts of water and slowly release it to both surface and ground water. • Ground water recharge is lost to the channeling of run-off into surface water and the filling of wetlands for development.
Eutrophication • Nitrates from fertilizers cause algae blooms; algae die off, increasing decomposition, which decreases oxygen levels, and kills fish. How does agricultural runoff (NO3) affect surface water?
Irrigate only or primarily at night • Irrigate with treated urban waste water • Cover irrigation ditches to prevent evaporation • Avoid growing water-thirsty crops in dry areas What are ways to conserve water through