PUB in practice: case studies - Runoff Prediction in Ungauged Basins: Synthesis across Processes, Places and Scales - page 273

Figure 11.2. Location map of the Krishna Basin. Photos, clockwise from upper left: north-west basin, on the Deccan basalts in the rain
shadow of the Western Ghats; central Deccan plateau on granitic outcrops and groundwater-irrigated rice paddy; the Krishna Barrage near
the mouth of the Krishna River, showing low hills of the Eastern Ghats; and portion of the Western Ghats mountains. Photos on left courtesy
of P. Thenkabail; photos on right: T. Biggs.

catchments within a single state, so regional comparisons
have not been performed, further limiting the potential for
prediction in ungauged basins. There is a critical need to
understand the main processes governing annual runoff pro-
duction in large river basins in India, and to quantify how
runoff is affected by spatial and temporal climatic variability.
Southern India has some distinct geographic features
that generate strong climatic and hydrological gradients.
The hydrological consequences of this strong spatial gra-
dient in precipitation are not well understood.
Therefore, the main research questions investigated were:

largest river by discharge. The river originates in the West-
ern Ghats, flows across the Deccan Plateau, and discharges
into the Bay of Bengal in the east.
The Krishna Basin, and peninsular India in general, is
characterised by large spatial gradients in rainfall caused
by the Western Ghats ( Figures 11.2 and 11.3 ). The West-
ern Ghats are relatively low-lying mountains, with eleva-
tions in the western part of the Krishna basin rarely
exceeding 1400 m. Despite this relatively low elevation,
rainfall in the Western Ghats exceeds 5000 mm/yr in some
locations, compared with less than 400 mm/yr to the east-
ern, leeward side. This very large rainfall gradient is
expected to have a large impact on the observed spatial
distribution of runoff. The spatial gradient in precipitation
is lower in the eastern part of the basin, where orographic
effects are reduced over the much smaller and less exten-
sive Eastern Ghats mountains, whose elevation rarely
exceeds 500 m in the eastern part of the basin.
The soils of the basin are generally thin Inceptisols,
Vertisols and Alfisols developed on the granites and
basalts of the Deccan Plateau. Bedrock outcrops are
common in some parts of the basin, with groundwater-
irrigated areas and small reservoirs in the valley bottoms

(1) Can a simple climatic index, calculated from satellite
imagery and interpolated meteorological data, predict
long-term runoff ratios over peninsular India?
(2) How much detail in the temporal and spatial distribu-
tion of climate is required to accurately predict
regional patterns in long-term runoff?

Description of the study area
The Krishna River basin drains 258 948 km 2 of southern
peninsular India (Biggs et al., 2007 )( Figure 11.2 ). It is the
fourth largest river basin in India by area, and the fifth