Kumar et al.,

spatially and temporally and improving the ability

Aliyar sub basin was chosen as the study area in this

of forecasting rainfall may help in planning crop

research, since the management of water resources

cultivation as well as in designing water storage’s,

in this basin has great importance in terms of a

drought management, planning drainage channels

wider range of water uses as well as downstream

for flood mitigation etc (Jayawardene et al. , 2008).

user requirements and environmental flows. Eight

The previous researchers stated that the climatic

rain-gauge (Anamalai, Aliyar Nagar, Attakatti,

change has an adverse effect on water resources

Chinnakallar, Pollachi, Topslip, Vettaikaranpudur

and rainfall pattern. Based on the above reports the

and Weaverly) stations were selected to study the

objective of the current study was framed to analyze

trends in the Aliyar sub basin (Figure 1).

the temporal pattern of rainfall trends on seasonal

and annual variation in Aliyar Sub basin.

Data collection and analysis

Monthly rainfall data of eight rain-gauge stations

Materilas and Methods

in the Aliyar sub basin for the period of 30 years

Study area

(1982-2012) had been collected from the office of

State Surface and Ground Water Data Centre, Public

Parambikulam-Aliyar basin is located in the south

works Department, Chennai. Statistical analysis of

western part of the Peninsular India covering areas

rainfall, identification of trends using Mann-Kendal

in Kerala and Tamil Nadu States. This basin area lies

test, estimation of magnitude using Sen’s slope

within the coordinates of North latitude between 10°

estimator, finally trend results were compared with

18’22” to 10°42’59” and East longitudes 76°48’37” to

regression analysis.

77°8’7”. The basin is drained by eight west flowing

rivers viz. Valaiyar, Koduvadiaru, Uppar, Aliyar

Rainfall analysis

and Palar (tributaries of Bharathapuzha river) and

The study area is situated in tropical monsoon

Parambikulam, Solaiyar and Nirar (tributaries of

zone having two distinct periods i.e.,1) Monsoon

Chalakudi river). The Aliyar River has its source

period spanning from June to December and 2)

in the Anamalai Hills. It flows in a north-westerly

Non-monsoon period spanning from January to

direction for about 37 kms in Tamil Nadu and enters

May. The monsoon period is further subdivided

into Kerala and finally confluence in Bharathapuzha.

into Southwest monsoon (June–September) and

Aliyar reservoir is one among the main components

Northeast monsoon (October–December). Similarly,

in PAP with a surface area of 6.50 km 2 and is formed

the non-monsoon period is also divided into winter

in the plains across the river with a gross storage

(January–February) and summer (March–May).

capacity of 109.42 mcm. The catchment area of

Rainfall analysis was carried out for all the seasons

the Aliyar dam is 196.83 km 2 . Apart from its own

as well as the whole year separately. The average

catchment, water can be diverted to this reservoir

seasonal and annual rainfall for each station of

through the Aliyar Feeder canal and the Contour

Aliyar sub basin has been computed by arithmetic

canal from the Parambikulam group of reservoirs.

mean method. The statistical parameters like mean,

Total area of sub basin is 574.75 km 2 and command

maximum, minimum, standard deviation, coefficient

area is 20,536 ha covering Pollachi (North), Pollachi

of variation, coefficient of skewness and kurtosis for

(South) and Anamalai blocks of Coimbatore district.

rainfall data have been computed for seasonal and

Crops grown in this sub basin area are coconut,

annual periods. Correlation coefficients between

sugarcane, banana, sapota, mango, fodder, besides

rainfall and time were also computed to determine

annual crops such as paddy, groundnut, cotton,

the strength of the linear relationship between the

vegetables, pulses, fodder, tomato, gaurds, Maize as

rainfall and time.

I crop, and Paddy and Groundnut as II crop.

38