Trend and Homogeneity in Subsurface Hydrologic Variables: Case Study in a Hard-Rock Aquifer of Western India - Hydrologic Time Series Analysis: Theory and Practice - page 174

and A ) of the Cumulative Deviations and the Bayesian tests indicate that 79,
82 and 88% of the sites have homogeneity in post-monsoon groundwater
level time series, respectively, but the R -statistic of the Cumulative Deviations
test shows that homogeneity is present in 97% of the post-monsoon groundwater
level time series.
It is apparent from Figs 8.6 and 8.7 that except for Bartlett and von
Neumann tests, all other tests indicate more number of sites with homogeneous
groundwater levels in post-monsoon season than in pre-monsoon season. The
large homogeneity in post-monsoon groundwater levels seems to be logical
because of limited human stress on the aquifer during monsoon/post-monsoon
season.
The homogeneity tests (Fig. 8.6) suggest that non-homogeneous sites
appear in three major clusters during pre-monsoon season over the study area
almost similar to the clusters found in case of trend tests. The first cluster is
in the northeast portion, second in southwest portion, and third in south portion
of the area. The factors responsible for non-homogeneities ( p < 0.05) in these
clusters could be explained based on the type of land use/land cover in the
area as discussed in Section 8.5.1. It should be noted that non-homogeneities
in the first and third clusters are due to non-systematic variation of groundwater
withdrawals for domestic and irrigation purposes, respectively (or
anthropogenic sources) since the clusters exist at the same location where the
clusters of significant increasing trends exist. However, non-homogeneities in
the second cluster may be attributed to geogenic factors. Almost similar types
of three non-homogeneity clusters are also discernible in post-monsoon
groundwater levels (Fig. 8.7) for the Link-Wallace test, Tukey test, Cumulative
Deviations ( Q -statistic) test, and Bayesian test (both U and A test-statistics).
However, these clusters are relatively less dense for the post-monsoon
groundwater levels compared to the pre-monsoon groundwater levels. The
lesser number of non-homogeneous groundwater level sites in post-monsoon
season is reasonable because of the fact that sufficient surface water is available
for domestic and agricultural purposes as well as groundwater supply is
augmented due to natural recharge, and hence, the underlying groundwater
system is almost free from artificial stress.
8.6 Trend and Homogeneity in Annual Net Recharge
8.6.1 Trends in Annual Net Recharge
Results of the three trend tests indicating number of sites with presence/
absence of trends in the annual net recharge are depicted in Fig. 8.8. This
figure shows that the number of sites having significant trends of increasing
net recharge (at D = 0.05) is almost same for the Mann-Kendall test (5%) and
the Kendall Rank Correlation test (6%). However, the Spearman Rank Order
Correlation test suggests that the annual net recharge has trends at 12% sites.