THE WORLD DELTA DATABASE

THE KRISHNA DELTA

Delta ID   #12.

Contributed by Huh et al, 2004.

LOCATION LAT. 15°54’N, LONG. 80°58’E

LANDMASS DRAINED INDIA, ASIA

BASIN OF DEPOSITION BAY OF BENGAL, INDIAN OCEAN

CLIMATE HUMID SUBTROPICAL (Caf)

AIR TEMP RANGE 20°C TO 30°C

TIDAL AMPLITUDE 1.8 M

DISCHARGE WATER 36,000M3/S

ID 7142049000030250, PATH 142 ROW 49

[MAGE ACQUIRED OCTOBER 28, 2000

Photographic album of the Krishna Delta slides

The climate of the drainage basin is dominated by the southwest monsoon which provides most of the precipitation for the whole region.  High water in the river is August - November and low water  is April - May [at Vijayawada].  Climatic types range from per-humid through dry sub-humid in the west through semi-arid in the central and eastern parts of the basin [Subramaniam et al 1882a, b]. Only in the very south central part of the basin truly arid.

The geology of the drainage basin is dominated in the northwest by the Deccan Traps, in the central part by unclassified crystallines  and in the east by the Cuddapah Group. The Dharwars [southwest central] and the Vindhian east central] form a significant part of the outcrops  within the unclassified crystallines. The deltaic region itself is formed  predominantly of Pleistocene to Recent material.

The drainage basin

The Krishna [historically also known as the Kistna] drainage basin originates near Mahabaleswar [1438 m.] in Maharashtra State within the Western Ghats.  Geologically this is the Dharwar [Karnataka] Craton, which is a Granite-Gneiss-Greenbelt massif. The provenance consists of Deccan Traps and the Dharwar Archean rocks. From its source the river flows east-north-east to the town of Wai for about 1280 kilometers and then east-south-east  for the last 80 kilometers, passed Sangli into Karnataka State and then Andhra Pradesh.  It final debouches into the Bay of Bengal. The total drainage length is 25,344 km. [Rao, 1964] with a total annual mean runoff of 55764 million cusecs and a maximum - minimum discharge of 33810 - 3 cusecs [Rao, 1975]. The total length is 968 km and it's drainage basin shares a common border with that of the Godavari River, which lies to the north.  The river drains 305,300 sq km (Figure 45). Drainage density is quite high  being 0.22 km stream length per 500 sq km.

About 75% of the basin is under a semi-arid [Dd] climate, receiving monsoonal rainfall. The rainfall of the delta is 910 mm with precipitation mainly in June through October.  The temperature is 22 - 27.5 - 34^oC [Hema Malini, 1979].

The deltaic plain

The Krishna delta is situated between ~15^o 42’ to 16^o 30’N and 80^o 30’ to 81^o 15’E. with it's head at Vijayawada.  The delta area is about 6,322 sq kilometers. After cutting the Eastern Ghats the river forms a deltaic plain some 95-km. wide before its four distributaries debauch into the Bay of Bengal. The first channel of the river starts near Avanigodda but the three main distributaries of the modern river splits into the Golumuttapaya, Nadimieru and Main channels.  A dam [weir] at the head controls the flow within the deltaic plain.  Vast amounts of material have been added during the past 50 years at the mouths of the distributaries with the formation of river mouth bars and barrier islands with associated back island lagoons.  As the delta prograded these lagoons were infilled with finer grained sediments. From Vijayawada to the Bay the average slope is 20 cm./km.  The delta itself has an area of ~4736 sq. Km.

The Krishna Delta has large tracts of Mangrove Swamps along the coast with maximum concentration surrounding the three main distributaries.  The common species are:

Rhizophora mucronata

Avicennia marina

Exoecaria agallocha

Cherodendron inerme.

Tidal flats occupy a considerable area of the lower deltaic plain especially between the Golumuttapaya and Avanigodda distributaries [Div island], although the tidal flats may be the product of a degraded inter-distributary bay between two, now abandoned, former channels.  

A series of grab samples taken for this project were used to measure sediment temperature and pH as well as water salinity as shown in the following table.

The marginal coastline

Bhanu Murthy  [199?] discussed the shelf deposits off the Krishna Delta. There is a very narrow continental shelf  [~15 km.] off the present Krishna delta when compared to adjoining portions of the coastal margin.  This is presumably a result of rapid progradation.  The hypsometric integral for the Krishna Delta is 0.36 which means the offshore slope is slightly concave suggesting a slight dominance of wave power over the discharge effectiveness of the river.  This value is similar to the Nile Delta which has a hypsometric integral of 0.37. The volume of the Krishna bulge is 9.93 cubic km. [using the Wright and Coleman formulae] and there is a Skewness ratio of 1.37 which indicates a pronounced littoral drift from the northeast towards Nizampatnam Bay [Vr=5.5 cu. Km. And Vl=4.18 cu. Km: Data from Coastal Studies Institute, LSU files].

Based on the Beach Ridge studies of K. N. Rao [1980] five [5] strandlines are recognized for the modern delta and at least seven [7] distributary lobes.

TABLE  [after Rao 1980]

The receiving basin

Two canyons are recognized off the mouth of the Krishna Delta: Nagarajuna Canyon and Machili Canyon.

Vibrocore studies of the Krishna Delta

Descriptive statistics