Usefulness of Compiled Geophysical Prospecting Surveys in Groundwater Research in the Metropolitan District of Quito in Northern Ecuador

Abstract

As in other large Andean cities, the population in the Metropolitan District of Quito (MDQ) in northern Ecuador is growing, and groundwater is becoming essential to meet the increasing urban water demand. Quito’s Public Water Supply Company (EPMAPS) is promoting groundwater research for sustainable water supply, and geophysical prospecting surveys are used to define aquifer geometry and certain transient groundwater features. This paper examines the usefulness of existing geophysical prospecting surveys in groundwater research in the MDQ. A database was built using 23 representative geophysical prospecting surveys compiled from EPMAPS’ public repository, official geotechnical research reports, and the scientific literature. Fifteen EPMAPS-promoted surveys used near-surface electrical techniques (seven used electrical resistivity tomography and eight used vertical electrical sounding) to explore Holocene and Pleistocene sedimentary and volcano-sedimentary formations in the 25–500-m prospecting depth range, some of which form shallow aquifers used for water supply. Four other surveys used near-surface seismic techniques (refraction microtremor) for geotechnical research in civil works. These surveys have been reinterpreted to define shallow aquifer geometry. Finally, four surveys compiled from the scientific literature used electromagnetic techniques (magnetotelluric sounding and other very low-frequency methods) to explore Holocene to late Pliocene formations, some of which form thick regional aquifers catalogued as the larger freshwater reservoirs in the MDQ. However, no geophysical prospecting surveys exploring the complete saturated thickness of the Pliocene aquifers could be compiled. Geophysical prospecting surveys with greater penetration depth are proposed to bridge this research gap, which prevents the accurate assessment of the renewable groundwater fraction of the regional aquifers in the MDQ that can be exploited sustainably.

Optimization of Q and R Matrices with Genetic Algorithms to Reduce Oscillations in a Rotary Flexible Link System

“…This technique focuses on solving the regulation problem, which is addressed by minimizing a quadratic index with a linear solution. Thus, LQR control aims to minimize the quadratic function or cost index to improve system performance [33]. It requires the controller to minimize a performance index of the form [34]…”

Integrated Geophysical Methods for Shallow Aquifers Characterization and Modelling

“…Since the call for papers was announced in June 2019, a total of 11 manuscripts were received. After a rigorous review process, eight papers have been accepted for publication [1][2][3][4][5][6][7][8]. To gain a better insight into the essence of the Special Issue, we offer brief highlights of the published papers below.…”

“…The paper "Usefulness of Compiled Geophysical Prospecting Surveys in Groundwater Research in the Metropolitan District of Quito in Northern Ecuador" [7] compiles and examines 23 geophysical prospecting surveys of interest in groundwater research in the Metropolitan District of Quito, including 7 ERT, 8 VES, 4 REMI and 1 FDEM surveys for shallow Holocene and late Pleistocene formations, and 3 L-MTS surveys for Holocene to late Pliocene formations. No surveys exploring the complete saturated thickness of the Pliocene aquifers could be compiled.…”