Lama et al.

and development (Strahler 1964, Kumar et al. , 2012,

mostly pre-Cambrian metamorphic and igneous

Panhalkar et al. , 2012, Yasmin et al. , 2013). Evaluation

rocks. The main rock formations of the study area

ofthemorphometricparametersrequirespreparation

are metamorphosed conglomerates, phyllites and

of drainage map, ordering of various streams,

quartzitesoftheShillongseries(TomarandSatapathy

measurement of the catchment area and perimeter,

2000. The watershed being a part of the Khasi hills

channel length, drainage density and a host of

has an undulating topography comprising of rolling

other parameters which help in understanding the

hills with steep slopes interspersed with valleys and

nature of the drainage basins (Sridhar et al. , 2012).

plateaus.

Geographical Information System (GIS) techniques

provideapowerfulenvironmentandtoolforanalysis,

manipulation and extraction of spatial information

for better understanding. It has been used to assess

various terrain and morphometric parameters of

drainage basins and watersheds (Chopra et al. , 2005,

Kar et al. , 2009, Sharma et al. , 2010, Sridhar et al. , 2012,

Wandre and Rank 2013, Aher et al. , 2014). Narendra

and Nageswara Rao (2006) carried out morphometric

analysis of Meghadrigedda watershed, Andhra

Pradesh, using GIS and Resourcesat-I data, while,

Vincy et al. , (2012) characterized the morphometric

parameters of two sub-watersheds of Meenachil

Figure 1. Location and drainage map of Um Shipra watershed

River in the western ghats of Kerala using GIS tools.

showing streams of different orders

In the present study, morphometric analysis of the

Soil erosion is an inherent problem because of steep

Um Shipra watershed located in Ri-Bhoi district of

hill slopes and high intensity of rainfall. The erosion

Meghalaya state in the north eastern part of India

has been further aggravated due to the prevalence

using GIS has been carried out with an objective to

of Jhum (Slash and burn agriculture) and Bun

study the drainage characteristics of the watershed.

cultivation (Raised bed method in which the beds

Materials and Methods

are made along the slopes) on the hill slopes. Though

the watershed receives plenty of rainfall during the

Study Area

monsoon season (more than 2000 mm), due to steep

slopes much of it is lost as surface runoff and only a

The Um Shipra watershed lies between 25° 40′ 14″ to

meager amount infiltrates into the ground. Streams

25° 44′ 10″ N latitudes and 91° 54′ 12″ to 92° 0′ 19″ E

are the major source of drinking water for the people

longitudes in Ri-Bhoi district, Meghalaya (Figure 1)

living in the nearby villages, as well as, for irrigation

and has a total area of 23.85 km 2 . The watershed is

and livestock uses.

characterized by humid, subtropical climate with an

annual average rainfall of 2416 mm, 80% of which is

Methodology

receivedduringthemonthsofMaytoOctober(Tomar

and Satapathy 2000. The mean monthly maximum

Thewatershedboundaryandtheassociateddrainage

and minimum temperatures normally range from

network from the Survey of India toposheets of

20.9 to 27.4°C and 6.7 to 18°C, respectively.

1:25,000 scale was digitized using the ArcGIS

software (Ver. 8.3) and the attributes were assigned

Geologically, the watershed is a part of the Shillong

to create a digital database. Using the hierarchical

plateau, which tectonically falls in the Central

ranking method (Strahler 1964) the stream orders

Assam Range. It is an old land surface made up of

were assigned and the digital database was updated

30