Latvijas hidroģeoloģiskā modeļa izveidošana Rīgas Tehniskajā universitātē (2010.–2015. g.)

Abstract

Hydrogeological models (HM) are developed in order to gain information that is needed for managing the protection and sustainable consumption of groundwater resources. The researchers of Riga Technical University (RTU) have developed two regional scales of HM of Latvia: in 1993-1996, REMO (Large Riga) and, in 2010-2012, LAMO1 (the first HM version). REMO covered the central part of Latvia and its plane approximation step was 4000 meters. LAMO1 encloses the ground territory of Latvia, the Gulf of Riga, and border areas with neighbouring countries (Estonia, Lithuania, Russian Federation, Belorussia). The HM plane step is 500 metres. Presently, the neighbouring areas of HM are not active. In the case of a transboundary projects the neighbouring country must provide hydrogeological data necessary to activate its neighbouring area. LAMO1 generalizes geological and hydrogeological data that have been accumulated by the Latvian Environment, Geology and Meteorology Centre (LEGMC). LAMO runs into the environment of licensed software Groundwater Vistas that is being used worldwide for modelling groundwater processes. In 2012-2015, LAMO1 was considerably updated, in order to improve the quality of results provided by HM. The LAMO2 version (2013) accounted for deep river valleys cutting the primary strata; the thick Devonian D2ar aquifer was replaced by the two aquifers and the aquitard that separated them; due to this innovation, the number of the HM planes increased from 25 to 27. In 2014, the LAMO3 version was obtained by increasing the density of the HM hydrogeological network (number of rivers and lakes, increased, accordingly, from 199 to 469 and from 67 to 127). For the current LAMO4 version, the plane step was reduced from 500 to 250 meters; the groundwater inflow for rivers was calibrated by accounting for information obtained from measurements of river flows. For LAMO1 and LAMO2, the permeability of primary aquifers (k-maps) was modelled by using a constant permeability value for an aquifer. In LAMO3 and LAMO4, more realistic k-maps were obtained by accounting for pumping data of wells. Presently, the latest LAMO4 version is being used by LEGMC and RTU specialists as the source of information on the geometry and permeability of geological strata, on distributions of groundwater heads and flows, on interaction between groundwater and surface water bodies (sea, lakes, rivers, precipitation). LAMO4 has been used by RTU researchers as a tool for investigating nature processes of the groundwater system of Latvia. The first results were quite unexpected, because it was found that the river watershed basin concept could not be used for the deepest strata of the basin. The research on LAMO3 and LAMO4 is supported by the Latvian state research program EVIDEnT.