Unit 5 Lesson 5 : Irrigation Methods

MCQ Practice

A farmer diverts water from a nearby river to flood her fields. Which of the following is not an issue associated with water diversion for agriculture? Answer: Decrease of sedimentation upstream

Drip Irrigation

Pros Very low evaporation rates (5%) Reduces nutrient leaching No land grading needed Cons Very expensive, clogs easily Requires mechanization Placement makes any other processes difficult

Spray and Drip Irrigation

Spray irrigation is moderately effective and moderately expensive. - Versatile - Less than 25% lost to evaporation Drip irrigation is very efficient, but very expensive - Less than 5% lost to evaporation - Once pipes are put down, they cannot be moved and are vulnerable to punctures and clogs

Environmental consequences of irrigation

Waterlogging - Remediate by allowing to dry out, amending soil with sand - Prevent with more efficient irrigation methods Salinization - Remediate by flushing soil with large amounts of water - Prevent with more-efficient irrigation methods Ogallala Aquifer - Location and significance - Generalize to consequences of aquifer overuse everywhere Saltwater intrusion -- only coastal aquifers

MCQ Practice

Which of the following irrigation methods is the most efficient use of limited fresh water supplies? Answers : Drip Irrigation

MCQ Practice

Which of the following irrigation-related problems would NOT require large amounts of fresh water for remediation? Answer : Waterlogging

Essential Knowledge

- The largest human use of freshwater is for irrigation (70%) - Types of irrigation include flood irrigation, furrow irrigation, drip irrigation, and spray irrigation. - Furrow irrigation involves cutting furrows between crop rows and filling them with water. This system is inexpensive, but about ⅓ of the water is lost to evaporation and runoff. - Flood irrigation involves flooding an agricultural field with water. This system sees about 20% of the water lost to evaporation and runoff. This can also lead to water logging of the soil. Spray irrigation involves pumping groundwater into spray nozzles across an agricultural field. This system is more efficient than flood and furrow irrigation, with only ¼ or less of the water lost to evaporation or runoff. However, spray systems are more expensive than flood and furrow irrigation and also requires energy to run. Drip irrigation uses perforated hopses to release small amounts of water to plant roots. This system is the most efficient, with only about 5% of water lost to evaporation and runoff. However, this system is expensive and so is not often used.

Flood and Furrow Irrigation

Agricultural water use for irrigation accounts for 70% of all water use Flood irrigation is easy to set up, but is inefficient and not suitable for all crops - Waterlogging, some salinization - 20% evaporation Furrow irrigation requires a modest investment and is more precise than flood irrigation, but is very inefficient - Salinization, soil erosion - 33% evaporation

Flood Irrigation

Pros - Easy - Inexpensive - Mechanization not required Cons - Requires water nearby - Not for all plant types - Land must be graded - Levees needed - 20% of water lost to evaporation - Waterlogging/salinization

Furrow Irrigation

Pros - Low investment - High sediment water can be used - Allows for some precision of application Cons - Not efficient on sandy soil - Difficult to apply small amounts - 33% of water lost to evaporation - Soil erosion

Spray Irrigation

Pros Precision application Supplements can be introduced into water Efficient - 25% or less lost to evaporation Can be programmed to run at certain times of day. Cons Larger up-front cost than flood/furrow irrigation Can include machinery run with electricity/ fossil fuels use Nozzles can clog Pivot systems can wear ruts in soil