Start with and integrate as needed the water right laws in India (see link below, plus any other directives). Hopefully your request will find needed help. Otherwise —Work with Indian water right specialists in the government. Obtain any rainfall or surface water records available, consult with communities and landowners. Develop supporting watershed data in GIS relative to geology, soils, land use, pollution issues, instream water needs, etc. Water agencies, universities, Professional Hydrologists and researchers may help.

https://nhrc.nic.in/sites/default/files/Right%20to%20water.pdf

You may consider contacting the Kerala State Electricity Board, the Kerala State Pollution Control Board, or the Kerala State Water Authority for information on surface water supply in the region. Additionally, you can also search for relevant government reports or data on websites such as data.gov.in or other government agency websites. You may also reach out to local universities or research institutions that conduct studies on water resources in the region. It is important to ensure that the data collected is reliable, up-to-date, and specific to the region you are interested in to build an effective water conjunctive management model.

The departments mentioned above by Mr. Ahmed certainly deal with water, but for different purposes like KSEB for electricity production, PCB for water quality monitoring, KWA for domestic water supply, etc. However if you want river discharge data, you have to approach Kerala Irrigation department or Central Water Commission at Thiruvanathapuram. You can also approach Agricultural department for crop details, irrigated areas, etc. You can also approach my parent organisation CWRDM at Kozhikode on water related information.