The reasons are erosion, over-irrigation and other practices that ruin farmland.

Water levels have been reduced by droughts and over-irrigation.

Poor grading practices and over-irrigation or leaking pipes exacerbate the tendency for landslides.

Poor drainage and over-irrigation causes the salts to collect on the surface, rendering large areas of land unsuitable for agriculture.

Intensified agriculture allowed for population increase, but also led to deforestation in upstream areas with resultant flooding and over-irrigation, which raised soil salinity.

In particular, by 1975 over-irrigation and poor drainage had led to waterlogging and salination, seriously damaging the soil in some places.

The causes include lack of site leveling to allow outflow of surface water, poor maintenance of drains and canals and over-irrigation by farmers.

The offences related to dairy effluent spilling from ponds, feed pads, a broken irrigator hose and sumps leading to over-irrigation of paddocks.

Much of the area is used as agricultural land and habitats are threatened by clearance leading to fragmentation, over-irrigation, and wildlife is vulnerable to introduced species such as foxes.

In the case of over-irrigation, salts are deposited in upper soil layers as a byproduct of most soil infiltration; excessive irrigation merely increases the rate of salt deposition.

Deep drainage (from over-irrigation) may result in rising water tables which in some instances will lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage.

The brilliant cultural centers of ancient Mesopotamia, for instance, are widely thought to have collapsed because of over-irrigation, which forced water tables to rise and carry salt to the surface, where it made land unfit for farming.

It is not particularly clear what caused the abandonment of Snaketown around 1100 C. E. Haury cites over-irrigation leading to soil depletion as a possibility for its fall, but still contends that abandonment also occurred in nearby cultures that were less dependent on irrigation.