The Daman Ganga, also called the Dawan River, is a river in western India. The river's headwaters are on the western slope of the Western Ghats range, and it flows west into the Arabian Sea. The river flows through Maharashtra and Gujarat states, as well as the Union territory of Dadra and Nagar Haveli and Daman and Diu. The Daman Ganga's main tributaries, the Daman and the Vag, run a course of and respectively before joining at Matunji to become the Daman Ganga River. A major part of the river lies in Maharashtra. Its total length from source to the Arabian Sea is . Some major tributaries which rise in and flow through the mountainous region of the states of Maharashtra, Gujarat and the Union Territory of Dadra and Nagar Haveli and Daman and Diu are the Dawan, the Shrimant, the Val, the Rayate, the Lendi, the Wagh, the Sakartond, the Roshni, the Dudhni, and the Piperiya. Daman is located on both banks of the river (Portuguese name: Rio Sandalcalo). At the mouth of the river the bar is a level bed made of hard sand, except for the North of the North point where the river enters the sea.
The river basin (part of the basin of west-flowing rivers from Tapi to Tadri), which lies entirely on the Western Ghats, has a total catchment area of . The catchment area's distribution is as follows: In the Nashik district of Maharashtra (60.74%); in the Valsad district in Gujarat (21.36%); and in the Union territory of Dadra and Nagar Haveli and Daman and Diu it is (17.90%). The mean annual runoff from the catchment is 3,771 million cubic metres. It is an inter-state multipurpose project of the Govt. of Gujarat and Union Territory of Dadra and Nagar Haveli and Daman and Diu (DNHDD). The storage of this project is shared by the riparian state of Gujarat and Union Territory of DNHDD as the beneficiary region. The total volume of water to be shared is 516.63 million cubic metres (MCM), 420.50 MCM for irrigation and the balance 96.13 MCM for other uses, which is allotted to the riparian state and Union Territories; Gujarat has a share of 399.19 MCM, Dadra and Nagar Haveli's share is 83.33 MCM and Daman's is 34.20 MCM. The composite dam is founded in an area with geological formations of amygdaloidal basalt, porphyritic basalt, dolerite, and agglomerate.
Daman Ganga-Pinjal River Linking Project
The Government of India's National Water Development Authority (NWDA) has proposed the Daman Ganga-Pinjal River Linking Project linking the Daman Ganga River to the Pinjal reservoir on the Pinjal River to the south, in the Vaitarna basin allowing surplus water from the Daman Ganga to be diverted south to Mumbai via the Pinjal reservoir. The feasibility report was prepared by NWDA in 2004, and in 2010 a tripartite agreement was signed between the Central government and the two state governments of Gujarat and Maharashtra. In January 2015, the project was approved for implementation.
Under this project the two reservoirs to be created by building dams are the Bhugad dam on Damanganga River in Gujarat and the Khargihill dam on the Vagh River near Behapada village in Thane in Maharashtra. The reservoirs will be linked by a pressure tunnel long and wide. The Bhugad-Khargihill and Khargihill-Pinjal tunnel which is totally in Maharashtra state is a long and diameter tunnel and will transfer the surplus waters to the extent of 909 MCM annually to Mumbai City to supplement the present domestic and industrial water supply system, from the Pinjal reservoir to Greater Mumbai; this part of the project is to be implemented as per plans evolved by the Municipal Corporation of Greater Mumbai (MCGM) and Mumbai Metropolitan Region Development Authority (MMRDA). The dam on the Daman Ganga at Bhugad will be a composite dam of in height and long, to create a gross storage of 426.39 MCM and a live storage of 400.00 MCM. The composite dam on the Vagh River at Khargihill is proposed to a maximum height of and in length with gross storage capacity of 460.79 MCM and live storage of 420.50 MCM. The Pinjal dam on the Pinjal River will be long and will have gross storage of 413.57 MCM and live storage of 401.55 MCM. The annual water diversion to greater Mumbai will be per second. The implementation of the entire project is planned to be completed over a nine-year period.
River pollution
The Damanganga River downstream of Vapi down to its mouth is polluted from the effluents emerging from the industrial and domestic wastes of Vapi town, Silvassa, Daman and Kachigaon. According to the Central Pollution Control Board's report the BOD value recorded at its monitoring station downstream of Kachogaon was a high of 30 mg/L. According to a study report of the Machhimar Adhikar Rahstriya Abhiyan due to the industrial effluents from Vapi town the dissolved oxygen level is very low<!--- ar 0.1-mg/1 ←—— What on earth is this? ---> and Mercury content in the groundwater in the town is about ninety-six times higher than the standards prescribed by the World Health Organization (WHO). Untreated effluents are directly discharged into the Damanganga and Kolak Rivers. This has resulted in pollution of the seawater to a limit of five nautical miles (9 km), seriously affecting fish life. The Common Effluent Treatment was also reported to be dysfunctional with about 1000 small-scale and artisanal fishermen in four to five villages getting affected on account of the Sarigam Industrial Association's effluent disposal pipeline.