The rainfall of Andhra Pradesh is influenced by both the South-West and North-West and North-East mansoons. The normal annual rainfall of the state is 925 mm. Major portion (68.5%) of the rainfall is contributed by South-West mansoon (June-Sept) followed by North-East mansoon (Oct.-Dec. 22.3%). The rest (9.2%) of the rainfall is received during the Winter and Summer months.

The rainfall distribution in the three regions of the state of the state differs with the season and monsoon. The influence of south west monsoon is predominant in Telangana region (764.5 mm) followed by Coastal Andhra (602.26 mm) and Rayalaseema (378.5 mm). Where as the the North-East monsoon provides a high amount of rainfall (316.8 mm) to Coastal Andhra area followed by Rayalaseema (224.3) and Telangana (97.1 mm). There are no significant differences in the distribution of rainfall during the winter and Hot weather periods among the three regions. The following Table gives a detailed picture of the rainfall distribution (monsoonwise and regionwise) during 1997-98.

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Andhra Pradesh is endowed with a variety of soils ranging from poor coastal sands to highly fertile deltaic alluviums. Red soils occupy over 66% of the cultivated area and are mostly situated in Rayalaseema districts. These soils have a low nutrient status. Red earths which are commonly termed as Red soils can be sub-classified as (a) Dubba soils (loamy sands to sandy loams) (b) Chalkas (Sandy loam soils) (c) Sandy clay loams (d) Loams including silty soils (e) Deep loamy sands and (f) Sandy loams with clay sub-soil. Chalkas occur mostly in the Telangana districts while red loams combined with sands are present in the upland regions of coastal districts.

Black soils cover nearly 25% of the cultivated area and are generally associated with poor drainage. They are also called as Regurs or Vertisols and are of two types. The first category in-situ soils while the other one is transported soils. While the first category can be noticed in the coastal districts and parts of Telangana and Rayalaseema, the second category occur in the valley regions of the slopes with calcareous concentrations. The in-situ soils are generally heavy in texture and high in salt concentration.

The alluvial loamy clay soils found in Krishna and Godavari deltas cover 5% of the cultivated area. The coastal sands occupy only 3% while the remaining 1% is covered by laterite soils in certain packets of the state.

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Andhra Pradesh has the advantage of having most of the East flowing rivers in the heart of the state bringing in copious supplies from the Western and Eastern Ghats and Deccan Plateau upto the Bay of Bengal. The major, medium and minor rivers that flow through the state number about 40. Of these, the most important river irrigation systems in Andhra Pradesh are (1) The Godavari (2) The Krishna (3)The pennar (4) The Vamsadhara and (5) Other minor coastal rivers.

Godavari borns at Triambakam near Nasik in Maharashtra and flows for 692 kms before entering Andhra Pradesh in Adilabad district. It flows through Eastern Ghats at Polavaram in West Godavari. At Dowlaiswaram in East Godavari where a barrage has been constructed by Sir. Arthur Cotton, where it gets divided into 2 branches, the Gautami and Vasishta, and finally merges in the Bay. The Godavari delta is formed in between these two. In Andhra Pradesh, Godavari flows through the districts of Adilabad, Nizamabad, Karimnagar, Warangal, Khammam, East Godavari and West Godavari. It is fed by number of tributaries and important among them are Pranahita, the Penganga, Wardha, Waiganga, Kinnerasani, Manjira, Sabari and Indravati. Most of the water in Godavari is contributed by Pranahita (40%), followed by Indravati (20%), Sabari (10%) and Manjira (6%). Almost two-thirds of the catchment of the Godavari flows into Bay of Bengal after traversing a total length of 1,446 kms. It has a catchment area of 3,10,692 sq.kms of which 23.62% lies in Andhra Pradesh. Ii.

Krishna river is the second largest river in the state. It flows 780 kms from Mahabaleshwar in Maharashtra before it enters Andhra Pradesh. The main tributaries are Koyna, Bhima, Ghataprabha, Mallaprabha, Tungabhadra, Yerla, Warna and Dudhganga. The river gets most of its water from Western Ghats. The catchment area of the river is 2,58,818 sq.kms., of which 29.45% is in Andhra Pradesh.

River Pennar also known as Uttara Pinakini enters Anantapur district of Andhra Pradesh after traversing 40 kms from Nandidurg hills of Mysore. The important tributaries of Pennar are Jayamangali, Chitravati, Kunderu, Papagni, Sagileru, Cheyyuru, Boggeru and Biraperu. It falls into Bay of Bengal 29 km. North of Nellore.

Vamsadhara river is the biggest of the river systems flowing from Eastern Ghats into Bay of Bengal mostly through Srikakulam district. It runs for 250 kms with a catchment area of 41,400 sq.kms.

There are 17 minor rivers flowing from Eastern Ghats to the Bay. Bahuda, Gosthani, Sarada, Varaha, Thandava, Pumpa and Swarnamukhi are the most important among them. The total surface water available from the river systems of Andhra Pradesh is estimated to be 2,746 TMC at 75% dependability. In the available total surface water about 1,900 TMC (69%) is being utilised presently.

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