MSc

Rain water harvesting is universally accepted as an important measure of water
conservation throughout the world. The quality of irrigation water has become a more
serious problem than quantity in different parts of the world. The characterization of
quality of water is crucial for assessing the suitability for i rrigation. Hence a study was
taken up on “Physico-chemical properties of rain water harvested under different
situations in lateritic soil’’ in the main campus of Kerala Agricultural University,
Vellanikkara during September, 2012 to August 2013. The objective of the study was to
compare the physico-chemical properties of rain water from different water sources in
lateritic soil. Water was collected from five sources viz, rainfall (RF), rain water
harvesting pond (RWH) , Kotteppadom pond (KP), well water (W) and surface runoff
(SR). The experiment for surface runoff study was laid out in an area with a gentle slope
between 5 – 10 per cent . Four rain pits were dug in this area with dimensions of 0.5 m x
0.5 m x 0.5 m and lined by polyethene sheet. Water samples were taken from these water
sources for one year at monthly intervals and they were analyzed for various physicochemical

parameters such as colour, turbidity, pH, EC, TDS, COD, BOD, SAR, RSC,
NO
3
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, Cl
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and Fe. The amount and distribution of rainfall received as well as the inflow to
the rain water harvesting pond were also studied. Soil samples were collected from around
rain-pits before and after rains and analyzed for the content of nutrients. The total quantity of rainfall during the study period was 2872.0 mm. The
maximum amount of rainfall was observed in June and the minimum in January, 2013.
The amount of rain water harvested in pond during the study period was 625.48 m
which
comes to 63 per cent of its storage capacity.
The quality of water from different sources was compared based on the results of
physico-chemical analysis. It was found that pH was highest (6.69) for water from
Kotteppadom pond during summer and lowest (5.54) for water from rainfall during post
monsoon season. The EC and TDS values were maximum for well water during pre-
monsoon season and there was significant difference among the different sources. There
was no significant difference among the sources of water as regards the content of Cl
and
NO
3
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over the different seasons. The values for BOD and COD varied significantly over
the different sources as also the seasons. Significant difference was observed for SAR and
RSC values among the different sources and seasons.
Loss of nutrients from soil via surface runoff from a sloppy area was studied. Soil
samples were analyzed for various physico-chemical parameters such as pH, EC, OC,
3 available N, P, K, Ca, Mg, Fe, BD, PD and WHC. The different parameters were
estimated both before and after receipt of rainfall. The mean values of these parameters
and percent changes along with t-value were found out. During summer, after the rains,
there were significant changes for the parameters like pH, OC, as well as available
nutrients like K, Ca, Mg, Fe, and the percentages of decrease were 1.67, 0.67, 37.94,
25.46, 5.62 and 8.85 respectively. The water holding capacity was also decreased by 4.80
per cent. During monsoon, available nutrients like N, P, K, and WHC decreased to the
extent of 23.68, 26.24, 49.32 and 7.29 per cent respectively.
In

general, it was found that the rainfall and rain water harvested in the water
harvesting pond were superior to well water, KP pond water and surface run off water.
Salinity was low for water from all the sources. Surface run off in an area with moderate
slope (5-10 %) resulted in loss of nutrients like K, P, Mg and Ca.
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