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Accueil du site → Doctorat → États-Unis → 2019 → Quantifying Groundwater Resilience and Impacts of Sediment Accumulation on Disconnection of Groundwater from Managed-Ephemeral Surface Water on a Basin Scale through Conjunctive Use for Irrigated Agriculture during Drought

New Mexico State University (2019)

Quantifying Groundwater Resilience and Impacts of Sediment Accumulation on Disconnection of Groundwater from Managed-Ephemeral Surface Water on a Basin Scale through Conjunctive Use for Irrigated Agriculture during Drought

Fuchs, Erek Hollis

Titre : Quantifying Groundwater Resilience and Impacts of Sediment Accumulation on Disconnection of Groundwater from Managed-Ephemeral Surface Water on a Basin Scale through Conjunctive Use for Irrigated Agriculture during Drought

Auteur : Fuchs, Erek Hollis

Université de soutenance : New Mexico State University

Grade : Doctor of Philosophy 2019

Description
Irrigation projects in arid, conjunctive use environments are especially impacted by reduced surface water supply because groundwater is often limited. Conjunctive use assumes groundwater resilience (i.e., ability to absorb pumping stress), but not necessarily in drought. Research regarding disconnection between interrelated surface and groundwater has evolved with attention to groundwater resilience, but practical methods to measure disconnection on a basin scale are lacking. Disconnection is also related to the average operational river stage, which may be physically limited by accumulated riverbed sediment. Consecutive surface water allotment shortages impacting the Rincon Valley within the Elephant Butte Irrigation District (EBID) in the arid, Lower Rio Grande Basin of south-central New Mexico, USA, are due to multi-year drought, and the effects are compounded by extraction of groundwater from the area’s uniquely constrained aquifer to meet crop requirements. The work described herein advances the water table fluctuation method by analyzing data from the EBID’s groundwater monitoring program to reveal the spatial and interannual variability of net aquifer storage changes over the last decade in the Rincon Valley, and introduces a new term, the groundwater-surface water ratio of application (GSRA). Quantification of aquifer resilience was found to enable the development of a GSRA range as a potential planning metric. Data from EBID groundwater monitoring wells and infiltration determined from river flows, including riverbed measurements along the Rincon Valley reach were used to determine net annual average discharge flux to the aquifer and pressure head below the River. Annual assessment confirmed that recent drought conditions shifted the system from connection to transition and then to disconnection. Nonlinear regression was used to quantify this shift to disconnection and back, which enabled determination of several disconnection process metrics, and was also used to confirm that nonlinear disconnection behavior was reversible without significant hysteresis. Results confirmed that an average total hydraulic head difference transition threshold can be determined from river/riparian monitoring sites over reach to basin scales and was extended to quantify the effects of hypothetical riverbed sediment excavation on disconnection, the average operational river stage, and the effects on aquifer recharge through the riverbed in the Rincon Valley.

Présentation (NMSU Library)

Aperçu document (ProQuest)

Page publiée le 13 octobre 2020