Evaluation of the response of a water table to a variable recharge rate

Abstract

A new method of evaluation of the response of a water table to artificial recharge is presented. The solution is formulated in the form of a simple numerical model. The model has several advantages over the traditional methods of mounding prediction. The effect of the unsaturated zone, which modifies the recharge rate as compared with the infiltration rate, is considered. Mounding is calculated for a variable recharge rate induced by a variable infiltration rate. Also, the effect of in-transit water in reducing the tillable pore space above a rising water table is considered. The validity of the model results is illustrated using several sets of field data collected in the Ghazvin Plain (Iran). Sample calculations proved that the model predicts mounding more accurately than the traditional methods and, therefore, more realistic recommendations for the design and operation of artificial recharge schemes are possible using the model. Evaluation de la réponse de la surface de la nappe phréatique à des taux variables de la recharge Résumé On présente une nouvelle méthode d'évaluation de la réponse de la surface de la nappe phréatique à la recharge artificielle. La solution est formulée comme un modèle numérique simple. Ce modèle a plusiers avantages par rapport aux méthodes traditionelles. On considère l'influence de la zone d'aération qui modifie le taux de la recharge par rapport au taux d'infiltration. La différence de niveau de la nappe est calculée pour un taux de recharge variable induit par un taux d'infiltration variable. Ainsi l'effet de l'eau en transit dans espace poreux de la zone d'aération qui surmonte la nappe d'eau ascendante est considéré. La validité des résultats du modèle est montrée par l'utilisation de plusiers séries de données pratiques collectées dans la Plaine de Ghazvin (Iran). Les échantillons calculés montrent que le modèle prédit plus exactement les résultats que les méthodes traditionelles et, par suite fournit des recommandations plus réalistes pour l'aménagement et l'exploitation de schémas de recharge artificielle.

Response of an Unconfined Sloping Aquifer to Constant Recharge and Seepage from the Stream of Varying Water Level

“…The transient rate of recharge is usually approximated by an exponential function or multiple linear elements (Zomorodi 1991;Rai and Manglik 1999). In this section, we define a cycle of recharge as follows:…”

Water table fluctuation owing to time-varying recharge, pumping and leakage

“…However, for short term recharge operations such as intermittent recharge or flood spreading, it would be more appropriate to consider time varying recharge to simulate the real field conditions with more accuracy. Zomorodi (1991) has shown that the analytical solution given by Dagan (1966) for constant rate of recharge failed to predict the declining trend of water table which is caused by a decrease in the rate of recharge. Rai et al (1994), Singh (1995, 1996), Rai et al (1998); Ramana et al (1995) have presented analytical solutions of linearized Boussinesq equation to describe water table fluctuation in response to time varying recharge.…”

Modelling of aquifer response to time varying recharge and pumping from multiple basins and wells

“…After drying and, if necessary, scrapping of the silted bottom of the basin high recharge rate closer to its initial value is rejuvenated again in the next phase of recharge operation (Bear, 1979;Detay, 1995;Mousavi and Rezai, 1999). Zomorodi (1991) has shown that the analytical solution of Dagan (1966) which is based on the assumption of constant recharge rate failed to predict the recession of the water table caused by a decrease in the recharge rate. Pumping of ground water is carried out at different times when need for irrigation arises.…”