Field-based estimation and modelling of distributed groundwater recharge in a Mediterranean karst catchment, Wadi Natuf, West Bank
<p>While groundwater recharge is one of the most prominently covered subjects in hydrogeology, the spatial distribution of recharge has been given relatively little attention, especially in semi-arid, karstic aquifers. Under conditions of highly diverse geology, relief, vegetation and land use...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-02-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/24/887/2020/hess-24-887-2020.pdf |
| Summary: | <p>While groundwater recharge is one of the most prominently covered
subjects in hydrogeology, the spatial distribution of recharge has been
given relatively little attention, especially in semi-arid, karstic
aquifers. Under conditions of highly diverse geology, relief, vegetation and
land use, the complexity and variability of spatially distributed
hydrological processes remains a challenge in many regions around the world.
This is particularly true for hitherto ungauged basins, such as Wadi Natuf,
a 103 <span class="inline-formula">km<sup>2</sup></span> large karstic Eastern Mediterranean watershed in the
Palestinian upstream mountain and recharge area of the Western Aquifer Basin
(WAB), which is shared with Israel in the coastal plain. In this first in a
series of two papers, distributed recharge is estimated and represented,
based on 7 years of extensive field observations and measurements and
based conceptually on observable physical landscape features such as
geology, land use and land cover (LU/LC) and especially soil conditions. For
the first time in the WAB, a forward calculated soil moisture and
percolation model (SMSP) was set up with parameters directly gained from
field observations. The model was parameterised in a strictly parsimonious
manner, as a one-dimensional model (a.k.a. “tank”, bucket or box model). This is
based on dominant hydrological processes, in particular saturation excess in
the soil column, and identifying patterns of linkage between different
landscape features. Average soil thickness was encountered at the range of
decimetres, rarely above one metre. Both soil thickness and LU/LC features,
such as terraced olive groves or forests as well as grassland or barren rock outcrops,
were found to be highly formation specific. This linkage allowed us to
further simplify the model and its requirements in a realistic manner for
eight soil moisture stations, chosen at six different geological formations
with typical soil and LU/LC representations. The main result of the model
was the determination of formation-specific recharge coefficients, spatially
ranging between 0 % and almost 60 % of annual rainfall or up to 300 <span class="inline-formula">mm a<sup>−1</sup></span> in Wadi Natuf's climate. The karstified main aquifers showed recharge
coefficients (RC) above 40 % and even the less prominent slightly
aquitardal local aquifers reached RC values above 30 %. The model was
separately tested on two conceptual levels: on the level of basin form
(soil moisture) and basin response (signatures of peak recharge and local
spring discharge events) under well-controlled conditions in isolated
sub-catchments. In principle, our approach is applicable in many of the
scarcely gauged karstic groundwater basins around the world with a highly
diverse landscape and geology.</p> |
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| ISSN: | 1027-5606 1607-7938 |