No abstract

U-pipes for ground source heat pump (GSHP) installations are generally inserted in vertical boreholes back-filled with pumpable grouts. Grout thermal conductivity is a crucial parameter, dominating the borehole thermal resistance and impacting the heat exchanger efficiency. In order to seal the borehole and prevent leakages of the heat carrier fluid, grouting materials are also hydraulically impermeable, so that groundwater flow inside the borehole is inhibited. The influence of groundwater flow on the borehole heat exchangers (BHE) performance has recently been highlighted by several authors. However groundwater impact and grouting materials influence are usually evaluated separately, disregarding any combined effect. Therefore simulation is used to investigate the role of the thermal and hydraulic conductivities of the grout when the BHE operates in an aquifer with a relevant groundwater flow. Here 3 main cases for a single U-pipe in a sandy aquifer are compared. In Case 1 the borehole is back-filled with the surrounding soil formation, while a thermally enhanced grout and a low thermal conductivity grout are considered in Case 2 and Case 3 respectively. Simulations are carried out maintaining the inlet temperature constant in order to reproduce the yearly operation of the GSHP system. For each of the 3 cases three different groundwater flow velocities are considered. The results show that a high thermal conductivity grout further enhances the effects of a significant groundwater flow. The conditions when neglecting the grout material in the numerical model does not lead to relevant errors are also identified.

Variable-density groundwater models require extensive computational resources, particularly for simulations representing short-term hydrologic variability such as tidal fluctuations. Saltwater-intrusion models usually neglect tidal fluctuations and this may introduce errors in simulated concentrations. The effects of tides on simulated concentrations in a coastal aquifer were assessed. Three analyses are reported: in the first, simulations with and without tides were compared for three different dispersivity values. Tides do not significantly affect the transfer of a hypothetical contaminant into the ocean; however, the concentration difference between tidal and non-tidal simulations could be as much as 15%. In the second analysis, the dispersivity value for the model without tides was increased in a zone near the ocean boundary. By slightly increasing dispersivity in this zone, the maximum concentration difference between the simulations with and without tides was reduced to as low as 7%. In the last analysis, an apparent dispersivity value was calculated for each model cell using the simulated velocity variations from the model with tides. Use of apparent dispersivity values in models with a constant ocean boundary seems to provide a reasonable approach for approximating tidal effects in simulations where explicit representation of tidal fluctuations is not feasible

No abstract

In the coming decades, the effects of expected climate change will affect key aspects of our society including quantity and quality of available water resources. It is believed that water resources will play a growing important role in Europe and in particular in the countries south of the Alps, where climate change could hit harder (EEA, 2014). Without appropriate interventions, water will turn from a good hearty undervalued to a scarce and precious resource, whose distribution will be less and less equitable, resulting in growing conflicts for its use. As already recognized by the European directives (2000/60/EC and 2006/118/EC), the theme of quantitative management of water resources is therefore a strategic issue that can allow the reduction of the risks and costs associated with climate change. Integrated management of both surface and groundwater for sustainable use nowadays represents more and more a key concern in environmental policies and water management. The goal of this work is to assess the effects on groundwater storage of a new management of irrigation waters. The highly variable availability of water resources during the hydrological season could be particularly troublesome in the management of irrigation systems, since they need water in seasons (spring-summer) when usually its availability has a depletion. Storage of groundwater in aquifers in colder seasons could be used to soften irrigation systems water deficit in drier ones. Specifically, the practice of "winter irrigation", i.e. the use of the main irrigation channels to recharge aquifers during the colder seasons, could increase water resource availability for irrigation during the drier growing seasons. A pilot groundwater flow transient model (MODFLOW2000, Harbaugh et al., 2000) with a domain of about 255 km2 was implemented in the north zone of Lodi Province, including a large part of the Consorzio Muzza irrigation district. The model was then run to estimate change in groundwater resource availability in two main scenarios: in the first scenario the storage in the shallow aquifer was computed in the colder period (October–March), when irrigation is not occurring; for this case, it was used measured monthly rainfall, average temperature for the period 2004-2013 (representing actual climate conditions) and an estimations of water volume used for irrigation. In the second scenario, an integrated management approach of irrigation and groundwater was tested, adopting "winter irrigation". Both scenarios want to assess if water storage in aquifers in colder periods could represent an additional water volume useful to mitigate possible climate changes effects on crops