Using a Distributed Recharge Model to Quantify Recharge Processes in a Semi-Arid Karst Catchment: An Example from Wadi Natuf, West Bank

Andrew Hughes,Denis Peach,Majdi Mansour,Nick Robins

doi:10.3390/w11020276

Abstract

The Wadi Natuf catchment is situated to the west of the Palestinian capital city of Ramallah which is in the West Bank. The catchment has been instrumented since 2003 to identify and examine recharge processes in semi-arid upland karst terrain, in which both direct and indirect recharge are important. The key recharge processes are direct rainfall recharge, and indirect recharge via wadis including the lateral routing of potential recharge in the unsaturated zone to springs which supply the wadis. A conceptual model describing these processes was developed. A distributed recharge model was then employed to test this conceptual model and to calculate recharge. A semi-arid wetting threshold method, based on local field experiments was used for recharge estimation. The model was calibrated by comparing simulated wadi flows to those recorded during a relatively short historical event. The study demonstrates that short-term monitoring can enable a sensible validation of a conceptual model leading to the estimation of recharge. Confidence in the model simulation requires further field work to strengthen the understanding of processes taking place in semi-arid climates and karstic flow environments.

Highlights

It is a self-evident truth that, at this time in the early part of the 21st century, water resources are under considerable pressure, from increasing urbanization [1]
The results presented are comparisons between modeled and measured soil moisture (Figures 5 and 6) for which the model was run from 20 January 2004 to 3 March 2004 on a daily time step and using the simple soil moisture deficit recharge calculation method
This method is most suited for temperate weather conditions, to estimate recharge values and to compare them with those estimated by the wetting threshold method

Summary

Introduction

It is a self-evident truth that, at this time in the early part of the 21st century, water resources are under considerable pressure, from increasing urbanization [1]. Population growth, the drift to urban centers, and the demand from sectors in the global economy such as agriculture, manufacturing, and energy, combined with environmental degradation and climate change, all place water resources under greater and greater strain To meet this demand, groundwater abstraction plays an important part in providing water for public and industrial supply around the world; aquifers are increasingly being exploited [2], as well as experiencing pressures from climate change [3]. One of the regions of the world where this problem is acute is the Middle East [4], where political instability compounds the challenge of ensuring sustainable water supply [5] In this region, groundwater plays an important role in providing water resources, mainly due to the arid nature of the climate and the geological setting. The nature of the terrain, with its steep slopes and karstic aquifers with a thick unsaturated zone [6,7,8,9,10], provides a challenge to both the understating and quantification of recharge

Objectives

Methods

Results

Discussion

Conclusion