Krishna Delta Research Articles

Do river deltas in east India retreat? A case of the Krishna Delta

The construction of multiple dams and barrages in many Indian River basins over the last few decades significantly reduced river flow to the sea and affected the sediment regime. More reservoir construction is planned through the proposed National River Linking Project (NRLP), which will transfer massive amounts of water from the North to the South of India. The impacts of these developments on fertile and ecologically sensitive deltaic environments are poorly understood and quantified at present. In this paper an attempt is made to identify, locate and quantify coastal erosion and deposition processes in one of the major river basins in India—the Krishna—using a time series of Landsat images for 1977, 1990 and 2001 with a spatial resolution ranging from 57.0 m to 28.5 m. The dynamics of these processes are analyzed together with the time series of river flow, sediment discharge and sediment storage in the basin. Comparisons are made with similar processes identified and quantified earlier in the delta of a neighboring similarly large river basin—the Godavari. The results suggest that coastal erosion in the Krishna Delta progressed over the last 25 years at the average rate of 77.6 ha yr − 1 , dominating the entire delta coastline and exceeding the deposition rate threefold. The retreat of the Krishna Delta may be explained primarily by the reduced river inflow to the delta (which is three times less at present than 50 years ago) and the associated reduction of sediment load. Both are invariably related to upstream reservoir storage development.

Improvement of groundwater quality due to fresh water ingress in Potharlanka Island, Krishna delta, India

Hydrochemical study had been carried out on the groundwater resources of Potharlanka Island, Krishna delta, India. Groundwater samples were collected and analyzed at 42 sites in December 2001 and October 2006. A comparative study of hydrochemical data indicates: groundwater is mildly alkaline with a pH of 7.0–8.2; electrical conductivity (EC) varies from 605 to 5,770 μS/cm in December 2001, and 652–5,310 μS/cm in October 2006. More than 62% of the groundwater samples in 2006 have TDS value <2,000 mg/l, which is within permissible limit of potable water, but 57% of the samples in 2001, are higher than the maximum permissible limit. Extremely low HCO3/Cl and variable high Mg/Ca (molar ratios) had been indicated the transformation of the fresh groundwater aquifer systems to saline in 2001. Groundwater of this Island is mainly classified as Na–Cl and mixed types. A high percentage of Na–Cl type of these waters indicates the possibility of seawater ingression/intrusion process during 2001 and comparatively mixed water type indicates the dilution activities of groundwater. Excessive withdrawal of groundwater has caused the increase of saline water intrusion. Improvement of groundwater quality in this Island due to artificial recharge structures made by NGRI under RGNDWM project and affects of the flood due to heavy rainfall of the months of September–October 2005 are discussed in this paper.

Use of hydrochemical parameters for the identification of fresh groundwater resources, Potharlanka Island, India

A hydrochemical study has been carried out on the fresh groundwater resources of Potharlanka, Krishna Delta, India. Groundwater samples were collected at 58 sites and analyzed in June and December 2001. The groundwater is mildly alkaline with a pH of 7.2–8.2, electrical conductivity (EC) varies from 645–4,700 μS/cm in June 2001 (pre-monsoon) and from 605–5,770 μS/cm in December 2001 (post-monsoon). More than 75% of the samples have >1000 mg/l TDS which is higher than the maximum permissible limit for potable water. Na and Cl are the dominating cations and these are directly proportional to TDS. Extremely low HCO3 /Cl and variable high Mg/Ca (molar ratios) indicated the transformation of the fresh groundwater aquifer systems to saline. Groundwater of this island is classified as Na–Cl, Na–Ca–Cl–HCO3, Na–Mg–Cl–SO4 and mixed types. A high percentage of mixed water types indicates the possibility of simultaneous fresh groundwater dilution activity along with a seawater ingression/intrusion process. Low rainfall and excessive withdrawal of groundwater has caused the increase of saline water intrusion.

X-ray mineralogical discrimination of depositional environments of the Krishna Delta, Peninsular India

ABSTRACT X-ray mineralogical analyses were applied to 107 surface and vibracore samples from the Krishna Delta of peninsular India to determine whether mineralogical assemblages produce distinct criteria for the recognition of modern deltaic subenvironments. Standard techniques were used to estimate the quantities of quartz, dolomite, K-feldspar, plagioclase, amphibole, calcite, clinoptilolite, and total clay mineral abundance in each sample. Clay mineral abundance in the m fraction was measured by a technique employing NEWMOD simulated patterns as standards. Discriminant function analysis was applied to 69 of the samples from eight subenvironments (lagoon, river mouth bar, mudflat, barrier island, mangrove swamp, foreshore, tidal creek, and channel) with 100% classification success when the whole-sample results included estimates of ideal clay-mineral layer types and a loss-on-ignition estimate of the organic content. The 38 additional samples were used as an overlay to provide a limited test of the canonical equations established by the first DFA analysis and also were 100% successful in the classification analysis. Most of the mineralogical changes can be attributed to grain-size sorting in the subenvironments of the delta. The major factors contributing to the success of the analysis are associated with quartz enrichment in the subenvironments falling within the marine-dominated part of the delta and smectite enrichment in the riverine-process-dominated subenvironments. The associations revealed by the study of this delta may be generally applicable to the discrimination of subenvironments in other modern and ancient deltas.

X-Ray Mineralogical Discrimination of Depositional Environments of the Krishna Delta, Peninsular India

X-Ray Mineralogical Discrimination of Depositional Environments of the Krishna Delta, Peninsular India

Mapping and monitoring prawn farming areas through remote sensing techniques

Coastal ecosystem is complex, sensitive and is subject to the influences of nature as well as human interferences. In recent years the prawn farming has increased significantly in the coastal areas of Andhra Pradesh, India, due to great demand in the export market at the coast of agricultural areas and mangrove forests which are essential for the coastal ecological balance. Hence, a study was carried out with the objective of mapping and monitoring the area under prawn farming and mangroves using multitemporal remotely sensed data along Krishna delta of Guntur and Krishna districts of Andhra Pradesh. Remotely sensed data from Landsat‐MSS pertaining to 1973, 1985 and 1990 years and Indian Remote Sensing Satellite‐1A (IRS‐1A) of 1992 are used for the study. The methodology adopted is digital analysis of multitemporal data. The study revealed that during 1985 to 1992 period the area under prawn farming increased significantly. Initially prawn cultivation started on a smaller scale on saline waste lands along the coast. Later due to commercialization of prawn culture, its cultivation has been extended into agricultural lands and mangrove forest.

Radiocarbon Ages of the Sub-surface Sediments in the Krishna Delta, India, and Their Geomorphological Implications.

The geomorphological study and the radiocarbon datings of the sub-surface sediments in the Krishna delta, indicate that the strandline around 2, 200 years ago was located at more than 40km inland from the present river mouth, and the delta tront has prograded more than 5km in the last 250 years. These facts differ somewhat from the previous view on the formation of the alluvial plain in the east coast of India that has been thought to be closely related to sea level oscillations since the Holocene maximum transgression. The rapid progradation of the delta front may be caused by human impact in the upper reaches of the Krishna river, and more detailed data are required to confirm this hypotheses.

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Geomorphological studies for disaster mitigation—a case study of the Krishna Delta, Andhra Pradesh, India

Abstract The geomorphology of an area plays a significant role in understanding the impact of cyclonic storms, in association with torrential rains, tidal waters, etc. Hence, the Krishna river delta area, which had been swept by at least 16 severe cyclonic storms and about 60 cyclones in the past 100 years, was selected for a case study. Geomorphological study of this highly cyclone prone delta of India, based on interpretation of Landsat-TM and IRS LISS-I and -II data on the scale 1:250000 has led to preparation of a flood hazard map. This flood hazard map, brings out very clearly the areas which are potentially safer, as well as those areas prone to different degree of flooding due to tidal waters, heavy rainfall, etc. Further, an attempt is made lo identify various causative factors responsible for the untold damage, which could have been averted. Poor dispersion of plumes near the drain/creek outfalls and presence of extensive standing flood waters provided a vital clue for identifying choked drains a...

Persians, Pilgrims and Portuguese: The Travails of Masulipatnam Shipping in the Western Indian Ocean, 1590–1665

The Coromandel port of Masulipatnam, at the northern extremity of the Krishna delta, rose to prominence as a major centre of maritime trade in the last quarter of the sixteenth century. Its growing importance after about 1570 is explicable in terms of two sets of events: first, the consolidation of the Sultanate of Golkonda under Ibrahim Qutb Shah (r. 1550–1580), and second, the rise within the Bay of Bengal of a network of ports with a distinctly anti-Portuguese character, including the Sumatran centre of Aceh, the ports of lower Burma, of Arakan, as well as Masulipatnam itself. Round about 1550, Masulipatnam was no more than a supplier of textiles on the coastal network to the great port of Pulicat further south, but by the early 1580s its links with Pegu and Aceh had grown considerably, causing not a little alarm in the upper echelons of the administration of the Portuguese Estado da Índia at Goa. The ‘Moors’ who owned and operated ships out of Masulipatnam did so without the benefit of carlazes from the Portuguese captains either at São Tomé or at any other neighbouring port, and while developing an intense trade within the Bay of Bengal, strictly avoided the Portuguese-controlled entrepot at Melaka. The Portuguese in the sixteenth and early seventeenth centuries were heavily involved in it in western India and a recent study has marshalled evidence from Portuguese sources on the mechanics of that trade in a port on the Kanara coast.2 In the seventeenth and eighteenth centuries, with the entry into the Indian Ocean of the large Chartered Companies, evidence on the grain trade is substantially increased, enabling us to see it in sharper focus in the broad canvas of Asian trade. the port was no more than a minor nuisance, and in the engagements that ensued, the Portuguese frequently had the worst of it, subsequently negotiating to recover prisoners lodged at Masulipatnam or at the court in Golkonda.2 However, by about 1590, the tenor of the relationship between the viceregal administration at Goa and the court at Golkonda had begun to show signs of change