Volumetric Uncertainty in an Open-Channel Water Delivery Network with Policy Implications
- Sanchez, Nadya
- Advisor(s): Lund, Jay
Abstract
The last twenty years has seen significant increases in water management regulations for irrigation districts in California. Surface water reporting and groundwater sustainability legislation have set new benchmarks for agricultural water agencies, including the 2009 surface water delivery law SBX7-7X. SBX7-7X mandates specific farmgate accuracy standards and farmgate-measurement-based volumetric billing for agricultural surface water delivery districts intended to improve water use efficiency.
Farmgates are typically part of dynamic open-channel networks, and improvements in farmgate hardware alone are not enough to achieve volumetric uncertainty benchmarks. It is also necessary to include delivery system uncertainties in parameters such as the water level, farmgate position, and the duration of delivery. This dissertation builds improved measurement gates into a dynamic canal network based on actual delivery system infrastructure and calculates total uncertainty based on varying levels of system stability.
The improvement in accuracy at the farmgate level is then compared to accuracy improvements at upstream aggregations in the system and a cost effectiveness function is developed. The relationship between cost at larger-volume and smaller-volume locations is called the granularity factor and represents the increase in cost for accurate measurement at small terminal points rather than more aggregated upstream flow locations in the system. The granularity factor is significant, representing the increased cost required to upgrade measurement infrastructure at thousands of smaller locations rather than dozens of larger locations.
The final chapters of the dissertation discuss the potential avenues for improved agricultural water use efficiency due to improved farmgate measurement and volumetric billing and consider the operational and organizational culture around water delivery. This analysis begins and ends with a deeper historical context of cropping and irrigation commons management by First Nations, settlers, farmers, and the state.