HU - Hydrogeology and Environment

Journal of the Dept. of Hydrogeology and Environment, University of Würzburg (ISSN 09309-3757)

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Vol. 35 (2010)




Abstract



Vol. 35: 

Water Resources and Dynamics of the Troodos Igneous Aquifer-system, Cyprus - Balanced Groundwater Modelling -



Joachim Mederer


Abstract:
The study investigates the water resources and aquifer dynamics of the igneous fractured
aquifer-system of the Troodos Mountains in Cyprus, using a coupled, finite differences
water balance and groundwater modelling approach. The numerical water balance
modelling forms the quantitative framework by assessing groundwater recharge and
evapotranspiration, which form input parameters for the groundwater flow models. High
recharge areas are identified within the heavily fractured Gabbro and Sheeted Dyke
formations in the upper Troodos Mountains, while the impervious Pillow Lava
promontories - with low precipitation and high evapotranspiration - show unfavourable
recharge conditions. Within the water balance studies, evapotranspiration is split into
actual evapotranspiration and the so called secondary evapotranspiration, representing the
water demand for open waters, moist and irrigated areas. By separating the
evapotranspiration of open waters and moist areas from the one of irrigated areas,
groundwater abstraction needs are quantified, allowing the simulation of single well
abstraction rates in the groundwater flow models.
Two sets of balanced groundwater models simulate the aquifer dynamics in the presented
study: First, the basic groundwater percolation system is investigated using twodimensional
vertical flow models along geological cross-sections, depicting the entire
Troodos Mountains up to a depth of several thousands of metres. The deeply percolating
groundwater system starts in the high recharge areas of the upper Troodos, shows quasi
stratiform flow in the Gabbro and Sheeted Dyke formations, and rises to the surface in the
vicinity of the impervious Pillow Lava promontories. The residence times mostly yield less
than 25 years, the ones of the deepest fluxes several hundreds of years. Moreover, inter
basin flow and indirect recharge of the Circum Troodos Sedimentary Succession are
identified. In a second step, the upper and most productive part of the fractured igneous
aquifer-system is investigated in a regional, horizontal groundwater model, including
management scenarios and inter catchment flow studies. In a natural scenario without
groundwater abstractions, the recovery potential of the aquifer is tested. Predicted future
water demand is simulated in an increased abstraction scenario. The results show a high
sensitivity to well abstraction rate changes in the Pillow Lava and Basal Group
promontories. The changes in groundwater heads range from a few tens of metres up to
more than one hundred metres. The sensitivity in the more productive parts of the aquifersystem
is lower. Inter-catchment flow studies indicate that - besides the dominant effluent
conditions in the Troodos Mountains - single reaches show influent conditions and are subflown
by groundwater. These fluxes influence the local water balance and generate inter
catchment flow. The balanced groundwater models form thus a comprehensive modelling system,
supplying future detail models with information concerning boundary conditions and intercatchment
flow, and allowing the simulation of impacts of landuse or climate change
scenarios on the dynamics and water resources of the Troodos aquifer-system.

Paper language: english; german abstract







 



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