Programs and policies are introduced to address a specific need. For example, we may observe that the incidence of diarrhea in a community is particularly high. This might be due to contaminated food or water, poor hygiene, or any number of plausible explanations. A needs assessment can help us identify the source of the problem and those most harmed.
For example, the problem may be due to the runoff of organic fertilizer which is polluting the drinking water used by certain communities.
Needs assessment is a systematic approach to identifying the nature and scope of a social problem, defining the target population to be served, and determining the service needed to meet the problem.
A needs assessment is essential because programs will be ineffective if the services are not properly designed to meet the need or if the need does not actually exist. So, for example, if the source of pollution contaminating drinking water is agricultural, investment in sanitation infrastructure such as toilets and sewage systems may not solve the problem. Needs assessments may be conducted using publicly available social indicators, surveys and censuses, interviews, etc.