Assessing Groundwater Level with a Unified Seasonal Outlook and Hydrological Modeling Projection

Jing-Ying Huang,Dong-Sin Shih

doi:10.3390/app10248882

Jing-Ying Huang, Dong-Sin Shih

Open Access

https://doi.org/10.3390/app10248882

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Abstract

Although the annual rainfall in Taiwan is high, water shortages still occasionally occur owing to its nonuniform temporal and spatial distribution. At these times, the groundwater is considered an acceptable alternative water source. Groundwater is of particular value because it is considered a clean and reliable source of fresh water. To prevent water scarcity, this study utilized seasonal forecasting by incorporating hydrological models to evaluate the seasonal groundwater level. The seasonal prospective issued by the Central Weather Bureau of Taiwan (CWB) was combined with weather generator data to construct seasonal weather forecasts as the input for hydrological models. A rainfall-runoff model, HEC-HMS, and a coupled groundwater and surface water model, WASH123D, were applied to simulate the seasonal groundwater levels. The Fengshan Creek basin in northern Taiwan was selected as a study site to test the proposed approach. The simulations demonstrated stability and feasibility, and the results agreed with the observed groundwater table. The calibrations indicated that the average errors of river stage were 0.850 for R2, 0.279 for root-mean-square error (RMSE), and 0.824 for efficiency coefficient (CE). The simulation also revealed that the simulated groundwater table corresponded with observed hydrographs very well (R2 of 0.607, RMSE of 0.282 m, and CE of 0.621). The parameters were verified in this study, and they were deemed practical and adequate for subsequent seasonal assessment. The seasonal forecast of 2018 at Guanxi station indicated that the 25th and 75th percentiles of simulated annual rainfall were within 1921–3285 mm and the actual annual rainfall was 2031 mm. Its seasonal rainfall outlook was around 30% accurate for forecasts of three consecutive months in 2018. Similarly, at Xinpu station, its seasonal rainfall outlook was about 40% accurate, and the amount of annual rainfall (1295 mm) was within the range of the 25th and 75th percentiles (1193–1852 mm). This revealed that the actual annual precipitations at both Guanxi and Xinpu station corresponded with the range of 25th and 75th percentiles of simulated rainfall, even if the accurate rate for the 3 month seasonal forecast had some error. The subsequent groundwater simulations were overestimated because the amount of actual rainfall was far lower than the average of the historical record in some dry season months. However, the amount of rainfall returned to normal values during the wet seasons, where the seasonal forecast and observation results were similar.

Highlights

Groundwater is the second-largest accessible source of freshwater after frozen water [1].Almost half of the world’s population has access to groundwater for drinking purposes, which is considered a cleaner and more reliable water source than other sources [2]
Prudhomme et al [4] described the development of Hydrological Outlook United Kingdom (UK) (HOUK), a seasonal hydrological forecasting service providing streamflow and groundwater level forecasts for the 3 months
To validate the parameters used in the model, a full-year simulation of 2017 was conducted

Summary

Introduction

Groundwater is the second-largest accessible source of freshwater after frozen water [1].Almost half of the world’s population has access to groundwater for drinking purposes, which is considered a cleaner and more reliable water source than other sources [2]. Groundwater is the second-largest accessible source of freshwater after frozen water [1]. Sci. 2020, 10, 8882 high groundwater table, whereas dry seasons may result in groundwater depletion and degradation in water quality [3]. Groundwater management should be taken in advance to preserve water resources before the groundwater reaches a deficient level [2]. Mackay et al [3] used seasonal rainfall forecasts and a lumped groundwater model in simulations to predict the groundwater level at 21 locations in the United Kingdom (UK) up to 3 months into the future. Prudhomme et al [4] described the development of Hydrological Outlook UK (HOUK), a seasonal hydrological forecasting service providing streamflow and groundwater level forecasts for the 3 months. Emerton et al [5]

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