I think more context would help with respect to your question. (Please)


Here are several examples of this usage in English. They are different enough that I could not choose among the suggestions above without more context about your specific text.


http://www.aquaengineering.com/si-rawwater.html
Aqua Engineering, Inc. has designed and seen successful implementation of many raw water systems. There is a resurgence in recent years of interest in utilizing raw or agricultural water, when available, to minimize potable water use for irrigation. Pump stations, storage facilities, delivery structures, measurement flumes and weirs, as well as the irrigation systems themselves are a part of these raw water systems

http://www.grundfos.com/web/grfosweb.nsf/Webopslag/F0F7F3EE7...
Constant operating optimisation of raw water catchment
Water utility companies are constantly on the lookout for ways to optimise water catchment and to reduce well field inspections.

When I/S Ikast Waterworks decided to build the new Bogild Waterworks and establish a new well field, the company therefore installed the most modern surveillance and control equipment available. ...


http://www.watercare.co.nz/default,111.sm

How is the raw water treated?
The water from the dams goes through a three-stage process: clarification, sand filtration, and chlorine disinfection.

The Waikato River water passes through four-stages: clarification, membrane filtration, granular activated carbon filtering, and chlorine disinfection.

Не думаю, что речь идет о неочищенной воде