Distributed memory parallel groundwater modeling for the Netherlands Hydrological Instrument

J Verkaik,J.D Hughes,P.E.V Van Walsum,G.H.P Oude Essink,H.X Lin,M.F.P Bierkens

doi:10.1016/j.envsoft.2021.105092

Abstract

Worldwide, billions of people rely on fresh groundwater reserves for their domestic, agricultural and industrial water use. Extreme droughts and excessive groundwater pumping put pressure on water authorities in maintaining sustainable water usage. High-resolution integrated models are valuable assets in supporting them. The Netherlands Hydrological Instrument (NHI) provides the Dutch water authorities with open source modeling software and data. However, NHI integrated groundwater models often require long run times and large memory usage, therefore strongly limiting their application. As a solution, we present a distributed memory parallelization, focusing on the National Hydrological Model. Depending on the level of integration, we show that significant speedups can be obtained up to two orders of magnitude. As far as we know, this is the first reported integrated groundwater parallelization of an operational hydrological model used for national-scale integrated water management and policy making. The parallel model code and data are freely available.

Highlights

Worldwide groundwater reserves, being of vital importance for more than 7 billion of people for drinking water, agriculture and industry (Wada et al, 2014), are threatened under changing climate conditions and increasing population
In this paper we focus on distributed memory parallelization of two of the five hydrological model codes that have been combined in the National Hydrological Instrument in 2013 (NHI): the model code for saturated groundwater and the model code for soil-vegetation water transfers in the unsaturated zone (SVAT), see De Lange et al (2014)
Concerning non-scalable algorithms, a more important explanation for the flattening of the fully-coupled Netherlands Hydrological Model (NHM) speedups can be found in the non-parallelized surface water model components which account for ~6% of the total run time

Summary

Introduction

Worldwide groundwater reserves, being of vital importance for more than 7 billion of people for drinking water, agriculture and industry (Wada et al, 2014), are threatened under changing climate conditions and increasing population Threats, such as extreme droughts and excessive groundwater pumping, are putting strains on national and regional water authorities to come up with adequate long-term plans for investments and adaptive measures leading to a sustainable and robust water management for the decennia to come. A number of high-resolution regional groundwater model ap plications were developed from 2000-2013 to support groundwater management by water boards and drinking water companies and eventually the model applications covered most of The Netherlands Under these developments, in 2005, the national and regional water authorities joined forces in unifying their modeling software and data, together with several national research institutes (former Alterra, Wageningen Environmental Research; former TNO-BGS and WL | Delft Hydraulics, Deltares; former MNP, PBL). For more than a decade, the NHI provides the Dutch water authorities and consultancies with a modeling environment used for answering actual water related questions, where the continuity of management and maintenance along with new de velopments of the modeling software and data is secured by the NHI consortium

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Discussion

Conclusion