Cal. Water Code § 35565.3

The district may conduct technical investigations and prepare analyses, studies, and reports pertaining to water supply, water rights, erosion, control of floods, storm patterns, water basin supplies, replenishment methods, water usage and water quality, soil characteristics, and other matters relative and necessary to the objective set forth in Section 35565.1. In order to carry out technical investigations, the district has the right of access to, and may, to the extent permitted by the California Constitution, enter upon, any lands within or without the district, with or without permission of the owner or owners of the land. The entry by the district or its authorized representative does not constitute, and does not give rise to, any cause of action in favor of the owners of the land, except for injuries resulting from negligence, wantonness, or malice.