K. Nageswara Rao

Landuse/Landcover change detection through remote sensing and its climatic implications in the godavari delta region

Interpretation of multi-date satellite imagery has revealed changes in land use/land cover pattern in the Godavari deltaic region during the past 26 years. The area under intensive agriculture has increased from 1459 to 3500 km2 and the extent of wetland from 368 to 648 km2 during the period 1973-1999, while the seasonal fallow has decreased by 2321 km2. Analysis of the climatic data of 1970-1998 from different stations covering the entire 5100 km2 area of the delta indicated that the day time temperatures have decreased by 0.2° C to 0.7° C, while the night time temperatures have increased by 0.5° C to 0.6° C during the past three decades. At the same time the rainfall has increased by about 75 to 479 mm. These trends in the climatic parameters arc attributed to the increased vegetation cover and wetland extent in the Godavari deltaic region.

Geomorphological implications of the basement structure in the Krishna-Godavari deltas, India

Summary. A correlation of the morphology of the Krishna-Godavari twin delta region with the tectonic framework of its basement along the east coast of India revealed that the Kolleru Lake in the inter-delta region is situated over a basement graben known as Gudivada Sub-basin, while the vast mudflat to the south of the lake coincides with the Bantumilli Sub-basin. The 8-km-wide beach ridge complex that separates the Kolleru and the southern mudflat largely coincides with the Kaja-Kaikaluru Ridge (horst) that lies in between the Gudivada and Bantumilli Sub-basins (grabens). The anomalous landward meandering of the Vasishta and Vainateyam distributaries close to the coastline and the three-fold widening during the past four decades of the Nilarevu estuary in the Godavari delta are in line with the Matyapuri-Palakollu Fault. Similarly, the 70-km-long straight segment of the delta-front coast between the Gautami and Vasishta distributary mouths in the Godavari delta, which is rather anomalous for a prograding delta, coincides with the landward boundary of the Ravva offshore sub-basin. Swerving of the Krishna River course throughout its deltaic reaches and the clock-wise bending of the active Krishna delta lobe into the Nizampatnam offshore sub-basin appear to be associated with the Krishna Cross Trend fault. Furthermore, the elongated nature of the Krishna delta and its visibly greater seaward bulge than its bigger neighbour (Godavari delta) in spite of the fact that the latter receives higher sediment loads and water discharges, might also be due to tectonic influence. Although the connection between the surface morphology and basement framework is hard to establish for want of detailed shallow subsurface data, the landform anomalies point to the possible influence of neotectonics in shaping the morphologies of the Krishna-Godavari deltas.

Remote sensing and gis applications in the identification of aquaculture hotspots at village level

Interpretation of IRS LISS II and LISS III imagery has revealed the various landforms as well as land use/land cover features in a part of the Godavari delta coastal belt. A comparative analysis of geomorphological vs. land use/land cover maps suggested that the landforms exert a certain degree of control over human land use activities even in this monotonously plain area. Further, an analysis of the sequential imagery pertaining to 1992 and 2001 aimed at detecting the land use/land cover change has indicated that the aquaculture has phenomenally increased by 9,293.5 ha during the 9-year period. At the same time, the cropland which occupied about 29,104 ha in 1992 has been reduced to 19,153.9 ha by 2001 mainly due to the encroachment of aquaculture. Village level data on temporal variation in land use/land cover extracted through GIS analysis revealed that in 14 out of the total 39 villages in the area, the conversion of cropland into aquaculture ponds was more than 30% with the highest conversion rate of 89.8% in Gondi village. These fourteen villages, which are designated as ‘aquaculture hotspots’ are grouped into 4 priority classes based on the intensity of conversion.