The impact of irrigation on human environment relates to the change in quality and quantity of soil and water as a result of irrigation and the effects of natural and social conditions in river basin and downstream of an irrigation scheme. The impact from the altered hydrological conditions caused by installation and operation of irrigation systems. The effects can be summarised as follows:

1. Direct Effect

An irrigation scheme draws water from groundwater, river, lakes and overland flows, and distributes it over an area. Hydrological or direct effects of doing this include reduction in downstream river flow, increased evaporation in the irrigated area, increased level in the water table as the ground water recharge in the area is increased and flow increase in the irrigated areas Likewise irrigation has immediate impact on the provision of moisture to the atmosphere, including atmospheric instabilities and increasing downwind rainfall.

2. Indirect Effect

Indirect effects are those that have consequences that take longer to develop and may also be long-lasting. The indirect effects of irrigation include the following:

• Water logging

• Soil salination

• Ecological damage

• Socioeconomic impact

The indirect effect of water logging and soil salination occurs directly on the land being irrigated. The ecological and socioeconomic consequences take longer to happen but can be more far reaching.

3. Adverse Effect:

The adverse effect includes:

• Reduce river flow.

• Increased ground water recharge, water logging and soil salinity.

• Reduced downstream river water quality.

• Affected downstream water users.

• Lost land use opportunities.

• Ground water mining with wells, land subsidence.