Quantifying Disconnection of Groundwater From Managed‐Ephemeral Surface Water During Drought and Conjunctive Agricultural Use

Abstract

The physics of disconnection between interrelated surface and groundwater has evolved considerably in recent years, especially since conjunctive use of water resources is increasingly dependent on groundwater resilience, but methods to measure disconnection on a river basin scale are lacking especially for managed‐ephemeral and irrigated‐agricultural systems. Multiyear drought limited surface water along Rincon Valley within the Elephant Butte Irrigation District (EBID) in the arid, Lower Rio Grande Basin of south‐central New Mexico, USA, and effects were compounded by continued extraction of groundwater to meet crop requirements. Average year‐end water table elevations in recent years have been below the average elevation of the riverbed, indicating potential disconnection between the river and the aquifer even when the river flows during the irrigation season. This study analyzed data from EBID groundwater monitoring wells adjacent to the river, infiltration determined from river flows, and riverbed measurements along the Rincon Valley reach to determine net annual seepage discharge to the aquifer and annual average pressure head below the river. Annual assessment from 2010 to 2017 confirmed that the drought shifted the system from connection to transition and then to disconnection. Nonlinear regression was used to quantify this shift to disconnection and back, enabled determination of several disconnection process metrics, and was also used to confirm that nonlinear disconnection behavior was reversible without significant hysteresis. The method developed herein confirms that the total head difference transition threshold can be determined from river/riparian monitoring sites over reach to basin scales.

Many Commonly Used Rainfall‐Runoff Models Lack Long, Slow Dynamics: Implications for Runoff Projections

“…For example, it could be stated that “the fact that a model cannot correctly predict groundwater dynamics does not mean that it cannot be used to predict streamflow,” and the only way to decide this is to consider auxiliary evidence of groundwater‐surface water interaction. Consider the following three possibilities: The streamflow and groundwater systems were “connected” both prior to and during the drought; The streamflow and groundwater systems were connected predrought, but became “disconnected” during the drought (see also Fuchs et al, ; Kinal & Stoneman, ); and The streamflow and groundwater systems were not connected predrought, nor during the drought. …”

“…The streamflow and groundwater systems were "connected" both prior to and during the drought; 2. The streamflow and groundwater systems were connected predrought, but became "disconnected" during the drought (see also Fuchs et al, 2019;Kinal & Stoneman, 2012); and 3. The streamflow and groundwater systems were not connected predrought, nor during the drought.…”

The Drying Regimes of Non‐Perennial Rivers and Streams

“…Limited regional coherence indicates a larger role of local physiographic and land cover/use characteristics in influencing drying characteristics than previously expected. Prior work has found numerous local characteristics influencing stream intermittency, including watershed storage (McDonnell et al., 2018; Nippgen et al., 2016; Tashie et al., 2020), subsurface heterogeneity (Herzog et al., 2019; Klaus & Jackson, 2018; Zimmer & McGlynn, 2017), land use change (Julian et al., 2015), and water withdrawals (Fuchs et al., 2019; Perkin et al., 2017). Potential drivers are explored in Section 3.3.…”

Assessing the Influences of Land Use Change on Groundwater Hydrochemistry in an Oasis-Desert Region of Central Asia

“…Meanwhile, groundwater hydrochemistry could be controlled by the coupling of multiple mechanisms, including evaporation-condensation, leaching and dissolution, precipitation, flushing and mixing, ion exchange, and subsurface biological activity [22,26,31,32]. Additionally, researchers found that spatiotemporal patterns of ion contents in groundwater can provide an insight into the salt origin, evolution, and migration pathways within the aquifers [26,33], which is helpful to understand groundwater water-salt migration in arid areas [34,35]. Yet, alteration of groundwater water-salt circulation by land use change and its influence on groundwater hydrochemistry evolution in the long term are not well known in the oasis-desert region of the Tarim Basin, particularly under the impact of cultivated area expansion.…”