What has been imposed by several irrigation districts since 2006 regarding water licenses?

The correct choice highlights the implementation of a moratorium on new water licenses by several irrigation districts since 2006. A moratorium typically refers to a temporary prohibition on a particular activity, which in this case is the issuance of new water licenses. This action is often taken in response to concerns about water scarcity, conflicts over water rights, or the need to assess the sustainability of current water use practices within the irrigation districts.

By halting the issuance of new water licenses, these districts aim to better manage existing water resources and ensure that they can meet the needs of current users without over-committing the available water supply. This approach can serve as a precautionary measure to protect the agricultural landscape and the ecosystem by preventing over-extraction of water from rivers and aquifers.

In comparison to the other options, which suggest introducing new licenses, suspending existing licenses temporarily, or increasing fees, the moratorium specifically addresses the overall management of water resources. It reflects a proactive stance to balance water allocation among users and sustain water availability for future generations. This context reinforces the significance of the correct answer.