Carlos Duque

Processes affecting groundwater temperature patterns in a coastal aquifer

The temperature depth profiles of six wells in the Motril-Salobren∼a aquifer were used as a basis for a comparative analysis involving various parameters to determine their relations and factors influencing the different trends. There is a clear influence of ambient temperature on all the profiles, with a lag time of two to five months. Nevertheless, there are clear differences in the temperature depth profile patterns that can be accounted for by other factors. First, there is a greater influence of localized recharge; Guadalfeo River as opposed to diffuse recharge; irrigation return flow and rainfall. Three of the wells located near the riverbed of the Guadalfeo River have extremely variable temperature-depth profiles and show clear river influence. In springtime, during the highest flood stages of the river due to cold melt water from the Sierra Nevada, the groundwater falls in temperature. During secondary peaks in river flow rates during the autumn due to rainfall, the warm water increases groundwater temperature. The effect of the river recharge decreases with distance from the course since there is less mixing with water from the Guadalfeo River. In addition, there are two temperature-depth profiles in which temperature variations remain shallow and follow a pattern that cannot be attributed to the influence of either of the above two parameters. Among these two cases, the most influential factor is the groundwater flow pattern typical of a discharge zone, characterized by vertical-flow components.

The Effects of Non-TIDAL Components, Depth of Measurement and the Use of Peak Delays in the Application of Tidal Response Methods

The efficacy and applicability of tidal response methods (TRMs) were assessed in terms of the techniques used, the, data used in the analysis, and the implementation of the methods under different conditions. The tidal efficiency (TE) and time lag (TL) methods were applied to directly measured groundwater head (GWH) values in the Motril-Salobreña coastal aquifer and compared with the same pre-filtered time series after eliminating the non-tidal signals through the continuous wavelet transform (CWT) procedure. The use of maximum and minimum groundwater peaks and sea-level peaks in combination to obtain different delay values and the effects of asymmetries in tidal fluctuations were assessed. Application of the TE method yields different D values when a complete groundwater head time series is considered, instead of the net induced tidal oscillation. Moreover, when the asymmetry of tidal oscillations is not taken into account, the application of TL may yield a higher uncertainty. In unconfined coastal aquifers, hydraulic diffusivity can be overestimated by the TE method if the non-tidal components are not removed from the measured time series of groundwater head. However, prior filtering provides better diffusivity results when the TE method is applied. The depth of the water head measurements leads to different D values when applying the TE method as a consequence of the changes in the specific storage with depth, which result from changes in pressure. The results of the application of the TL method depend on whether maximum or minimum peaks are used. Since the use of maximum peak delays can overestimate D, minimum peak delays are recommended, as they yield D values that are closer to the values obtained using the TE method.

Groundwater and Global Change in the Western Mediterranean Area

ed. This volume did not lead to long-term irreversible environmental effects, as evidenced by the recovery of the piezometric levels from 2007, reaching in 2010 a value similar to those before pumping (Fig. 4). Abstractions planned for the period 2017–2020 have been determined by the CHS taking into account the historical response of the aquifer in similar drought situations.

Groundwater Age Dating in Motril-Salobreña Coastal Aquifer with Environmental Tracers (δ 18 O/δ 2 H, 3 H/ 3 He, 4 He, 85 Kr, and 39 Ar)

The Motril-Salobrena coastal aquifer (SE Spain) is under high anthropogenic pressure due to the changes in river infiltration, irrigation and pumping. There are several uncertainties regarding how groundwater flows from the recharge areas to the discharge areas, and how long groundwater circulates in the aquifer due to the presence of layers with different hydraulic conductivity. This study constrains the age distribution in the aquifer by dating water samples taken at three different locations (recharge sector, intermediate sector and discharge sector) and at variable depths. The environmental tracers used were δ18O/δ2H, 4He, 3H/3He, 85Kr, and 39Ar. The groundwater dating allows to define the flow distribution and preferential flowpaths, to determine the mean groundwater residence times in the system and to establish the connection between age distribution and saltwater intrusion processes. Mean groundwater residence times range from recent to ~170 years, with the presence of young water in almost all the areas of the aquifer at a shallow depth and an age gradient at deeper locations in the discharge zone. The presence of the salt wedge increases the age mixing processes. The groundwater flow in the shallow part of the aquifer (0–50 m depth) turns out to be fast, with a residence time lower than 5 years, while the flow in the deeper parts (50–150 m depth) is slower and groundwater has at least 170 years.

Numerical Modeling of Groundwater Age Distribution in Motril-Salobreña Coastal Aquifer (SE Spain)

A mass and age transport numerical model of Motril-Salobrena coastal aquifer has been developed considering a new age dating survey with environmental tracers (3H–3He, 85Kr, and 39Ar). The method applied for the simulation of age transport was the direct age, which enables the direct simulation of the age defined as a transport specie. The model includes also variable density since saltwater encroaches from the sea boundary. The results of the model reproduce the saline wedge and the age distribution explaining the hydrodynamic processes in the discharge zone of the aquifer. The model describes the aquifer hydrogeological processes complementing the uncertainties of groundwater age dating, as well as the integration of other hydrogeological information from previous studies. The calibration based on the age dating yields a better fit of the advective-dispersive parameters than the common approaches using groundwater levels or concentrations and could be applied to other aquifers. This information will allow a better management of the water resources against the changes due to anthropogenic activity and climate change.

Mountain-front seismic acquisition and processing

This paper describes how BP and its partners successfully acquired 450 km2 of 3D seismic data in a complex area of the Llanos Foothills in Colombia. The data will be valuable for future decisions regarding the development of the Florena, Pauto, and Volcanera fields. The work area is in the Piedemonte Llanero, in the foothills of the Cordillera Oriental of Colombia. The stratigraphy involves Paleozoic, Cretaceous, and Tertiary rocks, and multiple regional unconformities. The main hydrocarbon accumulations are in the sandy levels of the Guadalupe Group and Mirador and Barco formations. The structural complexity of the foothills increases significantly from south to north, from relatively simple structures in Cusiana to tight asymmetric structures with higher dips in Cupiagua and Cupiagua South. Complexity continues to increase toward the north, where the shortening is greater as evidenced by surface geology (Figure 1).