dc.description.abstract |
A study was conducted to quantify baseflow deriving from the micro
watersheds of river Bharathapuzha lying near Valanchery town in the Malappuram
district of Kerala, named as Perassannur watershed (W1) and Painkannur watershed
(W2). Various baseflow separation methods such as graphical methods including
straight line, fixed base and constant base methods; UKIH and digital filter methods
including Lyne and Hollick (LH) and Chapman and Maxwell (CM) methods were used
for the quantification of baseflow. Their performance evaluations were done to find
the best suitable method for the selected study area. Micro watersheds were delineated
from SRTM DEM using GIS software and their geographical areas were found for
both the watersheds. Daily rainfall and stream flow were measured for both the micro
watersheds by digital rainfall event recorder and area velocity method respectively.
Morphometry of the study watersheds in terms of areal, linear and relief aspects; and
land use and soil analysis were made in the GIS platform to gain insights into the
parameters influencing the baseflow generation process. Graphical and statistical
comparisons were performed among the methods to identify the best filter parameters
for different filtering methods to make the baseflow separation process more accurate
and acceptable. Morphometric analysis showed that the maximum stream order of
Perassannur is 5 and Painkannur 4, and both of them have dendritic drainage pattern.
Most of the area of the watersheds was covered by cropland and paddy fields, which
facilitated the baseflow production. The value of N in the UKIH method was found as
4 in Perassannur and 3 in the Painkannur watersheds. Filter parameters of the digital
filter method were determined using the procedure given by Cheng 2016 and estimated
as 0.70 for Perassannur and 0.79 for Painkannur, and compared their performance with
the often used filter parameters with the values of 0.850 and 0.925 in which 0.925 gave
better results than the computed values for both watersheds. Estimated baseflow values
for each method were statistically compared with the observed base flow values to find
the best suitable method. Among the different filter methods, the LH method showed
better accuracy than other methods while the variable slope method has come out as
the most inaccurate procedure to estimate baseflow in the study region. |
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