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period 1965-2006 were collected from the Land Record Section of Collectorate,
Udaipur, Rajasthan. The collected rainfall data of the ten rainfall stations were
processed to prepare annual rainfall time series at each station. Pre- and post-
monsoon groundwater level data of 251 monitoring wells over the study area
for the 19-year period (1988-2006) were collected from the Ground Water
Department, Udaipur, Rajasthan; the location of sites are shown in Fig. 8.1.
All the collected groundwater level data were screened to check anomalies
and 140 monitoring wells were identified with continuous and unambiguous
records of pre- and post-monsoon groundwater levels for a period of 16 years
(1991-2006). Using 1991-2006 years data of groundwater levels, the annual
net recharge was calculated at 140 sites by water table fluctuation method.
8.3 Application of Time Series Tests
In this study, both graphical and statistical methods of time series analysis
were applied to determine spatial and temporal patterns in rainfall, pre- and
post-monsoon groundwater levels and net recharge time series. Trend and
homogeneity are two most important statistical characteristics of the
hydrological time series, which reveal temporal variability of hydrologic
variables (Machiwal and Jha, 2008). The GIS technique is used to present
spatial patterns of presence/absence of trend and homogeneity in the study
area. It is quite common to use only one or two tests for time series analysis,
which facilitates easy decision making. However, Machiwal and Jha (2008)
recommended that an adequate number of statistical tests must be applied for
detecting a particular time series characteristic and the results should be
analyzed critically to arrive at a reliable decision. Therefore, unlike the
customary approach, adequate/multiple statistical tests were applied in this
study in order to ensure realistic decisions about the time series analysis.
Firstly, spatial and temporal variations in annual rainfalls of ten rainfall
stations were analyzed using 43 years (1965-1997) data. Box and whisker
plots of annual rainfalls, which provide a summary of five statistical properties,
were drawn for ten rainfall stations and for 43 individual years. In addition,
annual rainfall time series of ten rainfall stations for the 43 years (1965-2007)
were analyzed for detecting trends by applying three most powerful statistical
tests, namely Mann-Kendall test, Spearman Rank Order Correlation (SROC)
test and Kendall Rank Correlation test. The details of these tests are given in
Chapter 4 (Section 4.3). Spatial homogeneity of the annual rainfall time series
was also examined by applying Levene's Analysis of Variance (ANOVA) test
and Levene's Median test. To carry out these time series analyses, spreadsheet
programs were developed using MS-Excel software.
Moreover, trend in the seasonal (pre-monsoon and post-monsoon)
groundwater level time series was examined by using above-mentioned
statistical tests. Homogeneity of the seasonal groundwater level time series
was investigated by using seven statistical tests, namely Hartley test, Link-
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