Risk Assessment for Safe Drinking Water Supplies - Global Drinking Water Management and Conservation - page 112

methods for the three stages of potable water supplies; these are source water
protection, water treatment, and pipeline distribution network. We also present a
brief assessment of case studies where risk assessment methods have been applied.
This chapter is organized as follows. Section 6.2 covers principles of source
water protection, for both point and nonpoint sources of pollution in greater detail
than covered in Chap. 2 . Section 6.3 covers the main approaches to risk assessment
for potable water supplies. Section 6.4 provides an overview of some risk assess-
ment case studies. Section 6.5 is a brief evaluation of the risk assessment process
and includes suggestions about types of risk assessment that are likely to succeed.

6.2 Source Water Protection

Effective water source protection requires an understanding of the concept of
watershed management and sources of water pollution (point and nonpoint) that
contribute to degradation of source water within the watershed.

6.2.1 Principles of Watershed Management

Surface water quality is affected by surface runoff that receives a variety of pol-
lutants. The application of watershed management is a useful tool for understanding
and controlling pollution of surface waters. As stated in Chap. 2 , a watershed is a
land area, a bounded hydrological system, within which all

flowing water bodies
such as rivers and streams merge in one outlet. A large watershed can be formed
from several smaller subwatersheds.
Developing a watershed management framework is necessary to minimize
adverse environmental problems in advance. The framework describes the goals,
outlines the protective actions, and focuses on a continued process for partners and
stakeholders to work together in supporting the watershed management plans
(USEPA n.d.). These partners and stakeholders make decisions on all aspects of the
framework including (a) water quality standards, (b) watershed management
approaches, and (c) individual management projects affecting localities and “ areas

of concern, where there is evidence of environmental stresses. Eventually, coor-

dinated efforts in watershed management facilitate economic development and the
implementation of environmental protection. Moreover, using sound science in
watershed management helps to achieve sustainable goals, such as environmental
cleanup or even relieving the pressure of water demand due to increasing urban
populations. A watershed is affected by a variety of factors that include geology,
hydrology, soils and vegetation, land use, and climate (USEPA n.d.). Furthermore,
watershed characteristics can change over time due to change in land and water use
patterns. Therefore, the watershed management framework should be adaptable to
change.

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