Evaluation of Simplified Stream‐Aquifer Depletion Models for Water Rights Administration

Abstract

We assess the predictive accuracy of Glover's (1974) stream‐aquifer analytical solutions, which are commonly used in administering water rights, and evaluate the impact of the assumed idealizations on administrative and management decisions. To achieve these objectives, we evaluate the predictive capabilities of the Glover stream‐aquifer depletion model against the MODFLOW numerical standard, which, unlike the analytical model, can handle increasing hydrogeologic complexity. We rank‐order and quantify the relative importance of the various assumptions on which the analytical model is based, the three most important being: (1) streambed clogging as quantified by streambed‐aquifer hydraulic conductivity contrast; (2) degree of stream partial penetration; and (3) aquifer heterogeneity. These three factors relate directly to the multidimensional nature of the aquifer flow conditions. From these considerations, future efforts to reduce the uncertainty in stream depletion‐related administrative decisions should primarily address these three factors in characterizing the stream‐aquifer process. We also investigate the impact of progressively coarser model grid size on numerically estimating stream leakage and conclude that grid size effects are relatively minor. Therefore, when modeling is required, coarser model grids could be used thus minimizing the input data requirements.

Effects of Streambed Conductance on Stream Depletion

“…For a given change in the head difference, a higher C leads to a greater degree of stream depletion and a lower C leads to a lesser degree of stream depletion [13,14]. The correlation between C and the stream depletion makes it an important model parameter in numerical stream depletion simulations (e.g., [9][10][11][12]18,19]). …”

“…However, Spalding and Khaleel [11] demonstrated that, despite their convenience, analytical approaches often fail to account for conditions that exist in natural steam-aquifer systems. Since that time, numerical groundwater models have proven to more accurately estimate stream depletion as they can better account for the complex nature of true systems [12][13][14][15][16].…”

Influence d'un plan d'eau de surface sur la vulnérabilité de l'eau pompée d'un puits en milieu rural /

“…Des exemples sont décrits par Sophocleous et al (1995), Conrad et Beljin (1996), et Chen et Shu (2002 …”

Evaluation of the streambed leakage concept in analytical models using data from three pumping tests

“…This concept was developed more out of mathematical convenience than sedimentologic concepts, but it is still widely applied (Anderson and Woessner 1992). Numerical studies found that the assumption of a fully penetrating stream may lead to an overestimation of stream depletion, and the solutions are highly sensitive to changes in the streambed conductance coefficient (e.g., Sophocleous et al 1995;Conrad and Beljin 1996). However, no insight was provided in the validity of the streambed conductance concept in streamaquifer models.…”