R&D highlights edition 2019

PROJECTS Water and subsoil resources 38 T he Republic of Guyana is located in the Northeast of South America, with Venezuela to the west, Surinam to the east and Brazil to the south. The country is very rich in water, which is why Guyana is known as “the land of many waters” in the indigenous language. From a geological point of view, the country can be divided into two parts: the flat, low-lying, young coastal area in the north and the very old hinterland, which is one of the oldest formations on the surface of the world. Ninety percent of the population live on or near the coast, extracting groundwater for consumption and industry. In recent years, pressure on the groundwater reserves has risen due to the large increase in groundwater extraction and saltwater intrusion into the formation. BUILDING UP KNOWLEDGE ABOUT GEOHYDROLOGY IN GUYANA: FROM FIELDWORK TO WATER MANAGEMENT Deltares was called in to work on a programme for sustainable water management in Guyana. The first phase of the programme was the training of engineers and staff to collect geological data. In four months, 100 wells were logged, analysed, interpreted, visualised and stored in the IMOD database. Deltares became involved in a project to construct new groundwater wells in Guyana involving close collaboration with the Dutch drilling company De Ruiter Grondwatertechniek. We organised a workshop in 2017 at the national water company Guyana Water Incorporated (GWI), where we presented an overview of activities designed to raise the knowledge level and manage the freshwater aquifers better. The outcome of this workshop was that GWI asked Deltares to present a general approach for water management with a focus on GWI building up knowledge itself rather than letting Deltares take over all the activities. The first phase in this general approach is to increase the knowledge of geology and geohydrology in Guyana, during which process geological and geohydrological data are being collected. The focus in the first phase was on collecting geophysical well log data from 100 wells. During hands-on workshops and courses, GWI engineers were trained to perform geophysical well logs themselves, and the GWI staff were trained to interpret logs and visualise them. In four months, all 100 wells were logged, interpreted, visualised and stored in the IMOD database. This data can be used to analyse individual wells and cross-sections can be made to establish a picture of the geological setting. By adding geological knowledge and the positions of the wells, one can visualise the aquifer in a step towards understanding the geohydrology in the coastal area. All the geophysical well log data and well lithologies are digitally available in the iMOD package, making it a valuable dataset for the development of future groundwater models. These models and new knowledge can be used to make decisions about where and how much water can be extracted in a sustainable way. Contact: Pieter Doornenbal, Pieter.Doornenbal@deltares.nl, t +31 (0)6 1215 2212 Marco de Kleine, Marco.deKleine@deltares.nl , t +31 (0)6 25034108 Well locations where geophysical measurements were collected during the 2018 field campaign 3D fence diagram showing formation and wells

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