Assessment of water quality and quantity of springs at a pilot-scale:
Applications in semi-arid Mediterranean areas in Lebanon
Abstract
This work presents an integrated methodology for the assessment of
threats on spring quality and quantity in poorly investigated
Mediterranean semi-arid karst catchments in Lebanon. Pilot
investigations, including 1) high-resolution monitoring of spring water
and climate, 2) artificial tracer experiments, and 3) analysis of
micropollutants in surface water, groundwater, and wastewater samples
were conducted to assess flow and transport in three karst catchments of
El Qachqouch, El Assal, and Laban springs. First, the high-resolution
in-situ spring data allows the quantification of available water
volumes, as well as their seasonal and yearly variability in addition to
shortages and floodwaters. Moreover, the statistical analysis of
hydrographs and chemographs helps assess the karst typology, spring type
and hydrodynamic behavior (storage versus fast flow). Furthermore, a
series of artificial tracer experiments provides information about
key-transport parameters related to the intrinsic vulnerability of the
pilot springs, while the analysis of micropollutants gives insight into
the specific types of point source pollution as well as contaminant
types and loads. On the one hand, the tracer experiments reveal that any
potential contamination occurring in snow-governed areas can be observed
at the spring for an extensive time due to its intermittent release by
gradual snowmelt, even with enough dilution effect. On the other hand,
the assessment of persistent wastewater indicators shows that springs in
the lower catchment (including El Qachqouch) are highly vulnerable to a
wide range of pollutants from point source (dolines and river) and
diffuse percolation. Such contaminants breakthrough is challenging to
predict because of the heterogenous duality of infiltration and flow,
typical of karst systems. Finally, this set of investigations is
essential for the proper characterization of poorly studied systems in
developing areas, whereby results can be integrated into conceptual and
numerical models to be used by decision-makers as support tools in
science-evidenced management plans.