Water Resources - Primitive Methods

1. Uneven distribution of rain .places like assam, bengal get 150-250 cmsrajasthan rarely gets even 25 cms
2. Seosanal rainfall.rains are concentrated over 4 month period while rest of the year is dry. Irrigation can help multiple cropping.
3. Agricultural season extends over winter, but most parts in india have dry winter. Irrigation allows year long cultivation.
4. Monsoons in india are uncertain. late or early arrival affects crop production severly. irrigation helps from this irregularity.

1. Primitive methods - well, tanks and inundation canals
2. Modern - tube wells , canals, multi purpose projects

ADVANTAGES :1. Simplest and cheapest source of irrigation.
2. They can be dug at any convenient place
3. Independent source of irrigation and may be used as and when need arises
DRAWBACKS:1. During summers wells dry up and fail to provide water when its most needed.
2. a well can water only a limited amount of land , around 1-2 hctrs.
3. In many parts well water is brackish.

1. Walls are constructed across a stream or depression and rainwater collects here during rainy season.
2. Ground below the tank should be rocky to prevent percolation of water.
3. Tanks vary in size but most are small.
4. popular in AP, TN, WB, oriisa , karnataka

1. Hard rocks underlying in large areas of deccan do not allow easy percolation of water.
2. The undulating surface forms natural depressions and these hollows may have simple dam across them.

ADVANTAGES:1. Tanks enable people to store water which are in abundance during rains , which would have otherwise flowed out uselessly .
2. Tanks help in raising the underground water level of wells found in surrounding areas.
3. Apart from irrigation in many villages tanks form the only source of water.
DISADVANTAGES1. Tanks occupy large surface area which could otherwise have been used for cultivation2. Many tanks dry up during the dry season and fail to provide water when most needed3. Silting of tanks is a problem and de-silting of tanks is needed.

1. These canals are flood water canals and have water in them only when river is flooded.2. They are solely dependent on rainfall for its supply3. These canals are taken out from rivers without any regulating system like wiers.4. Many inundation canals are being converted into perennial canals.