Irrigation Module 5 PDF

Irrigation CE 308 – Hydrology Prepared by: Engr. Lagrada  1 2 3 Intended Discuss the Identify Demonstrat Learning fundamental principles of infiltration factors...

Irrigation CE 308 – Hydrology Prepared by: Engr. Lagrada  1 2 3 Intended Discuss the Identify Demonstrat Learning fundamental principles of infiltration factors affecting infiltration e the use of selection and Outcomes computation and its rates in a importance in watershed; sequence for the and infiltration. hydrologic cycle; irrigation  Irrigation  It is the process of applying controlled amounts of water to plants at needed intervals.  Irrigation helps to grow agricultural crops, maintain landscapes, and revegetate disturbed soils in dry areas and during periods of less than average rainfall. Irrigation 2  TYPES OF IRRIGATION METHODS Surface: water applied by gravity across the soil surface by flooding or small channels Sprinkle: water applied at the point of use by a system of nozzles with water delivered to the sprinkler heads Micro: water applied to the point of use through low pressure, low discharge devices (ex: drip, bubblers, micro sprayers) Subirrigation: water made available to the crop root system by upward capillary flow through the soil profile Irrigation 3 Factors Factors considered for Irrigation considered System for irrigation system Crops to be grown Environmental concerns Topography of physical site Soils conditions Farming equipment Water supply Costs Climate Energy available Chemigation Operation and management skills 4  Irrigation Water Quantity Rivers in natural and regulated regimes Local surface flow coming to estuaries Groundwater taken from dug wells Household and Industrial wastewater, mine water, seawater Requirements: Water must be usable for irrigation Water reserves and flow rate must satisfy the needs of water Source should be located close and upstream to the given irrigation area Irrigation 5  Irrigation Water Quality Based on physical and chemical characteristics of water Good quality river water for irrigation successfully used Water quality problems Salinity : salts in soil or water reduce water availability to the crops yield affected Water infiltration rate : high sodium to low calcium ratio reduces the infiltration rate affects irrigation and yield Specific ion toxicity: certain ions from soil or water accumulate in a sensitive crop to concentration high enough to cause crop damage Irrigation 6  Irrigation Water Quality Guidelines Irrigation 7  Irrigation Method Selection Soil type: Sandy soil low storage capacity and high infiltration rate Frequent and small irrigation applications required Sprinkler or drip more suitable than surface irrigation Loam or clay soils - all three types can be used Clay soil with low infiltration rate - ideally suited to surface irrigation Slope: Sprinkler or drip preferred on steeper or unevenly sloping lands Little or no land levelling required Irrigation 8  Irrigation Method Selection Climate Strong wind can disturb the spraying of water from sprinklers High wind conditions drip or surface irrigation methods preferred In areas of supplementary irrigation, Sprinkler or drip irrigation more suitable than surface irrigation Due to flexibility and adoptability for varying irrigation demands Water availability Water application efficiency generally higher for drip and sprinkler systems Especially preferred under water short conditions Irrigation 9  Irrigation Method Selection Type of crop Surface irrigation –for all type of crops Sprinkler and drip –cash crops due to high investment (ex: vegetable and fruit trees) Drip irrigation –irrigating individual plants or trees or row crops (ex: vegetables and sugarcane) Irrigation 10  Irrigation Method Selection Type of technology Drip and sprinkler technically more complicated methods Purchase of equipment's require more capital cost Regular supply of fuel and spare parts to be maintained Irrigation 1 1  Irrigation Requirement It is the amount of water required by a crop in a given period of time of their normal growth field conditions. It includes evapotranspiration not met by effective precipitation and other economical unavoidable losses such as surface runoff. Irrigation 13  Irrigation Requirement The climate: in a sunny and hot climate, crop needs more water per day than in cloudy and cool climate. The crop type: crop like maize and sugarcane needs more water than millet and sorghum. Growth stage of crop: fully grown crop needs more water than the crops at initial growth stages. Irrigation 15  Irrigation Requirement Evaporation: process by which liquid water is converted into water vapor from evaporating surface Transpiration: process by which water vapour leaves the living plant body and enters into atmosphere Evapotranspiration: quantity of water transpired by plants plus the moisture evaporated from the surface of the soil and vegetation Potential evapotranspiration: ET that occurs when the ground is completely shaded by actively growing vegetation and where there is no limitation in the soil moisture Irrigation 16  Irrigation Requirement Field Irrigation Requirement is expressed as: − 𝐷𝑝 − 𝐹𝐼𝑅 𝐷𝑒 = 𝑡 𝐷𝑝𝑙 𝐸𝑎 𝐷𝑒𝑡 = depth of evapotranspiration Where: 𝐷𝑝 = depth of precipitation 𝐷𝑝𝑙 = depth of precipitation as surface 𝐸𝑝𝑎 = irrigation runoff/infiltration 𝐷 − 𝐷 𝑝𝑙 = effective rainfall depth = effi ciency 𝐷 Irrigation𝑝𝑒 17  Irrigation Requirement 𝐷𝑒𝑡 = 𝐾𝐸𝑝 Potential Evapotranspiration: Irrigation Efficiency, Ea: Soil Class Irrigation Effi ciency, Ea (%) Sand 60 Where: 𝐷𝑒𝑡 = depth of evapotranspiration Sand Loam 65 Loam 70 𝐾= crop coeffi cient Clay Loam 75 𝐸𝑝 = pan evaporation Heavy Clay 80 Irrigation 18  Irrigation Requirement Crop coefficient, Kc This value varies greatly with stages of crop. Four main stages Initial Crop Development Mid-season Late season Irrigation 20  Irrigation Requirement Effective Rainfall Depth 𝐷𝑝𝑒 = 0.8𝐷𝑝 − 25, if 𝐷𝑝 > 75mm/month 𝐷𝑝𝑒 = 0.6𝐷𝑝 − 10, if 𝐷𝑝 < 75mm/month *Note: 𝐷𝑝𝑒 is always equal to or greater than zero and never negative. Both 𝐷𝑝 and 𝐷𝑝𝑒 are in mm/month. Irrigation 21  Sample Problem Using the data given in the table for a given crop, determine the field irrigation requirement for each month assuming irrigation efficiency to be 60 percent. Depth of Month Crop factor, K Pan Evaporation, Effective rainfall, evapotranspiration, FIR(mm) Ep (mm) Dp-Dpl (mm) Det (mm) November 0.2 118.0 6.0 December 0.36 96.0 16.0 January 0.75 90.0 20.0 February 0.9 105.0 15.0 March 0.8 140.0 2.0 Irrigation 22 Thank you.