Sharavati is a river which originates and flows entirely within the state of Karnataka in India. It is one of the few westward flowing rivers of India and a major part of the river basin lies in the Western Ghats. The famous Jog Falls, located about 25 km from Siddapura, is formed by this river. The river itself and the regions around it are rich in biodiversity and are home to many rare species of flora and fauna.
Origin and topography
The river Sharavati originates at a place called Ambutheertha in the Thirthahalli taluk. According to ancient legend, the god Rama shot at the ground with his Ambu (translates to bow and arrow) because his wife, Sita, was thirsty. When his arrow hit the ground, water poured out (translates to Thirtha) and quenched her thirst. Because the river, according to the legend, originated with this event, the river is called "Sharavati" as "Shara" translates to arrow.
The total length of the river is around and it joins the Arabian Sea at Honnavar in Uttara Kannada district. On its way, the Sharavati forms the Jog Falls where the river falls from a height of 253 m. The river is dammed at Linganamakki; the portion of the river above the dam is upstream and the remaining is downstream. The major tributaries of the river are Nandihole, Haridravathi, Mavinahole, Hilkunji, Yennehole, Hurlihole, and Nagodihole. Sharavati river basin falls into two districts of Karnataka namely Uttara Kannada and Shimoga. The upstream river basin is extended to two taluks i.e, Hosanagar and Sagar. The entire basin has an area of with upstream being and the downstream being .
Geology
The river basin mainly consists of Pre-Cambrian rocks. The two major groups of rocks found in the Sharavati river basin are the Dharwar system and the peninsular gneiss. The Dharwar system: This system contains metamorphic rocks that are considered to be among the oldest in India. These rocks are derived from ancient sediments like conglomerates, ferruginous quartzites, greywackes, schists and limestones. They are rich in iron and manganese. Peninsular gneiss: These are crystalline rocks and are made up of granite, granodiorite, granito-gneiss, migmatite etc.
Soils in the Sharavati basin are mainly lateritic in origin and tend to be acidic and reddish to brownish in colour. The various type of soil found here are clay loamy, clayey, clayey-skeletal, and loamy. Four soil orders are found in the upstream river basin: ultisols, alfisols, inceptisols and entisols.
Climate
Rainfall
With a major part of the river lying in the Western Ghats, the Sharavati river basin receives a large amount of rainfall. Mean annual rainfall ranges from 6000 mm in the western side to 1700 mm in the eastern side of the basin. About 95% of the rainfall is received during the month of June to September (July being the rainiest) when the southwest monsoon is at its peak. There is some rainfall in the post monsoon season in the form of thundershowers mostly during October and some rainfall also occurs during the summer months of April and May.
Temperature
April is usually the hottest month with the mean daily maximum temperature at 35.8 °C and the mean daily minimum at 22.2 °C.
Humidity
During the morning, the relative humidity exceeds 75% for most times of the year. During the months of monsoon, the relative humidity during the afternoons is approximately 60%. During the driest months (January to March), the relative humidity in the afternoon is less than 35%.
Dams
Linganamakki dam
The Linganamakki dam located in the Sagar taluk has a length of and was constructed across the Sharavati river in 1964. It was designed to impound 4368 million cubic meter of water in an area of around , submerging of wetland and of dry land, the remaining being forest land and wasteland. The dam's height is above sea level. The total capacity of the reservoir is 152 TMC (Thousand Million Cubicfeet). It has a catchment area of nearly . It receives water mainly from rainfall and also from the Chakra and Savahaklu reservoirs, which are linked through Linganamakki through a canal. The water from Linganamakki dam flows to Talakalale Balancing Reservoir through a trapezoidal canal with a discharge capacity of 175.56 cubic metres per second. The length of this channel is about 4318.40 m with a submersion of . It has a catchment area of about . The gross capacity of the reservoir is 129.60 cu meters.
Gerusoppa dam
The Gerusoppa dam project was completed in 2002 with the main purpose of generation of electricity. It was constructed near the Gerusoppa village in the Uttara Kannada district. It has a height of 56 metres and a length of 545 metres.