Final answer:
It is true that lowering the water table in areas underlain by unconsolidated or weakly consolidated strata can cause land subsidence. The extraction of groundwater can result in soil compaction and subsidence, and maintaining the current level of the water table is critical for the ecosystem and preventing geological and water supply issues.
Step-by-step explanation:
It is true that in areas underlain by unconsolidated or weakly consolidated strata, lowering of the water table can cause the land to subside. This phenomenon, known as subsidence, occurs due to the loss of support for the ground's surface when the volume of groundwater is reduced, leading to a compaction of the soil or sediment. For example, when groundwater is extracted, especially in large amounts, such as for a new housing development with its own drilled groundwater wells, the water table can lower over time, potentially causing subsidence.
Regarding the proposed development near a river, there are several anticipated effects on the local environment due to the withdrawal of groundwater. The new wells will likely create cones of depression, lowering the adjacent water table and possibly affecting the nearby rancher's well by reducing the water available to it. This can also lead to decreased water levels in the river, which can have detrimental impacts on the ecosystem relying on it. It's critical to maintain the current level of the water table to prevent these negative outcomes, preserve the health of the riparian area, and forestall subsidence.
Furthermore, maintaining the pre-development level of the water table is essential due to environmental concerns such as supporting wetland ecosystems that rely on specific water flow conditions and preventing saltwater intrusion in coastal areas. Natural recharge during wetter periods helps to maintain a balanced water table, but excessive withdrawal, especially in areas with unconsolidated or weakly consolidated strata, can lead to long-term degradation of both land stability and water availability.