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 177

monsoon groundwater levels and net recharge time series. The box and whisker
plots for the mean annual rainfalls reveal that long-term variation in the
rainfall is the highest at Kotra rainfall station. The annual rainfalls in some of
the years at Dhariawad and Kotra stations are substantially higher than the
rainfalls at other stations. The results of trend tests indicate the presence of
significant declining trend at Mavli rainfall station. The results of the Levene's
ANOVA test suggest that the rainfall over the study area is spatially
homogeneous. Overall, the spatial and temporal variations of annual rainfall
in the study area are not statistically significant. Also, no trend was detected
in the annual rainfall series except at single rainfall station.
The results of the seven homogeneity tests and the three trend tests for
groundwater level time series in both pre- and post-monsoon seasons indicate
that non-homogeneous sites appear in three dense clusters over the study area:
(i) in northeast portion (dominated by residential area), (ii) in southwest portion
(dominated by hillocks), and (iii) in south portion (dominated by cultivated
command). The non-homogeneity in groundwater levels in the first and third
clusters is attributed to anthropogenic factors, and that in the second cluster is
due to geogenic factors. It is also found that the non-homogeneity and trend
are present at relatively large number of sites in the pre-monsoon season
compared to that in the post-monsoon season.
The results of two homogeneity tests, viz., Link-Wallace test and Bayesian
test for the annual net recharge time series are almost similar. It is also found
that the annual net recharge time series are relatively more homogeneous
compared to the pre- and post-monsoon groundwater level time series. The
results of the Mann-Kendall test and Kendall Rank Correlation test for trend
detection are almost similar. Homogeneity and trend tests suggest that the
annual net recharge time series is homogeneous without any trends in a major
portion (more than 90% sites) of the study area.
Overall, it is concluded that the Tukey, Link-Wallace, Bayesian tests and
Q -statistic of the Cumulative Deviations test are superior to other homogeneity
tests. Further, it is recommended to use either Mann-Kendall test or Kendall
Rank Correlation test for exploring trends in similar future studies.
References
Bhuiyan, C., Singh, R.P. and Kogan, F.N. (2006). Monitoring drought dynamics in the
Aravalli region (India) using different indices based on ground and remote sensing
data. International Journal of Applied Earth Observation and Geoinformation ,
8(4): 289-302.
Broers, H.P. and van der Grift, B. (2004). Regional monitoring of temporal changes
in groundwater quality. Journal of Hydrology , 296: 192-220.
Buishand, T.A. (1982). Some methods for testing the homogeneity of rainfall records.
Journal of Hydrology , 58: 11-27.