Slide 1

Irrigation - definition - necessity -advantage disadvantages(11th Feb 2013)

Fresh water 3%

Periods of water resources renewal on the Earth Water of Hydrosphere Period of renewal World Ocean 2500 years Ground water 1400 years Polar ice 9700 years Mountain glaciers 1600 years Ground ice of the permafrost zone 10000 years Lakes 17 years Bogs 5 years Soil moisture 1 years Channel network 16 days Atmospheric moisture 8 days Biological water several hours

Utilization of Water Resources

ROOTING CHARACTERISTICS AND MOISTURE USE OF CROP

DefinitionIrrigation is the controlled application of water to croplands. Its primary objective is to create an optimal soil moisture regime for maximizing crop production and quality while at the same time minimizing the environmental degradation inherent in irrigation of agricultural lands.ORIrrigation is the application of water to the soil to supplement natural precipitation and provide an environment that is optimum for crop production. Irrigated crops produce more food.

Irrigation may be defined as the artificial application of water to the root zone of the crop at right time and in required quantity for the optimum growth of agricultural crops so as to get more crops per unit of water used. 11

Following factors are important:

NECESSITY OF IRRIGATIONThroughout the crop period adequate quantities of water is required near the root zone of the plants for their growth Insufficient Rainfall Uneven Distribution of Rainfall Improvement of Perennial CropsDevelopment of Agriculture in Desert Area 16Irrigation is artificial application of water to the root zone of the crop at right time in required quantity for optimum crop yield. 17FUNCTIONS:Supplies moisture to the soil essential for, germination of seeds and chemical and bacterial processes during plant growth.Cools the soil and the surroundings thus making the environment more favorable for plant growth.Washes out or dilutes salts present in the soil.Softens the clods and thus helps in tillage operations. Enables application of fertilizers.Reduces the adverse effects of frost on crops.Ensures crop success against short duration drought.Normally natural Plants can grow with basic requirements like Forests but to have better and earlier we need additional18IrrigationWhat? artificial application of water Where to apply? to the root zone of the cropWhen to apply? at right timeHow much to apply? in required quantityWhat for?for optimum crop yield

19ADVANTAGES OF IRRIGATION Stabilised Yield of CropsProtection from Famine Improvement of Cash CropsProsperity of FarmersSource of revenueNavigationHydroelectric Power Generation.Water SupplyGeneral CommunicationDevelopment of Fishery20DISADVANTAGES Rising of Water Table Formation of Marshy Land Dampness in Weather Loss of Valuable Lands 21

MEASUREMENT OF WATER

Water is measured - at rests and in motion.

Water at rest- reservoirs, ponds, tanks volume units - litre - l- cubic metre m3 - hectare- centimetre ha-cm - hectare- metre ha-m. 24Duty of water - expression - relationship between duty and delta, Rooting characteristics and Moisture use of cropWater in motion - rivers, canals, pipeline, field channels

Rate of flow - litre per second - lps- litre per hour - lph - cubic metre per second - cumec - cubic foot per second - cusec

DUTY OF WATER (d ha/cumec)The area that can be irrigated with a continuous non-stop supply of irrigation water at the rate of one cumec or cusec throughout the base period. It is expressed as acre/cusec or hectare/cumec. BASE PERIOD (B days)The period over which irrigation water is to be supplied for the production of any crop.

Normally this is equal to the period between the first and last irrigation to a crop.DELTA ( cm)The depth of water required by a crop during the crop season to meet its requirements. This does not have any relevance to the area of the cropped field. It is expressed in mm or cm.RELATIONSHIP BETWEEN DUTY, DELTA AND BASE PERIOD

Let be the depth of irrigation water required by a crop in cm B be the base period in daysd be the duty of water in ha/cumec.Then, The volume of water required per ha of cropped field = x 10000 = 100 m 100

The base period = B days = B x 24 x 3600 = 86400 B secondsThe term duty explains that to irrigate d ha of land water is to be supplied at the rate of 1 cumec.

Therefore,To irrigate one ha the rate of flow required = 1/d cumec.

The volume of water supplied @ 1/d cumec over B days = 86400 B/d m3 Equating the volume required and supplied, we get,100 = 86400 B di.e., = 864 B dFactor affecting duty of waterChoice of the cropChoice of the VarietyConveyance efficiency of the irrigation systemTypes of the ChannelTypes of the regulating devices.Total area to be irrigated.Total volume of water availableGROSS DUTY OR INTAKE DUTY Area irrigated by each cumec of water let down at the head works of an irrigation system

NET DUTY OR DELIVERED DUTY.Area irrigated by each cumec of water delivered at the field margin of an irrigation system

Efficiency of the irrigation system = Net duty /Gross duty.