The relationship between input and output of water across a defined system boundary, e.g. a watershed or the project site boundary. If input > output, then storage within the system increases; if input < output, then storage decreases. (DRET, 2008).
Source: Identifying and assessing water sources: Guidance document for the onshore oil and gas industry, International Petroleum Industry Environmental Conservation Association (IPIECA), 2014. Global Standards