Proc. IAHS, 383, 261–266, 2020https://doi.org/10.5194/piahs-383-261-2020© Author(s) 2020. This work is distributed underthe Creative Commons Attribution 4.0 License.

Open Access

Hydrologicalprocesses

andw

atersecurityin

achanging

world

A review of the adaptability of hydrological models fordrought forecasting

Zikang Xing1,2,3, Miaomiao Ma2, Zhicheng Su2, Juan Lv2, Peng Yi1,3, and Wenlong Song21State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,

Hohai University, Nanjing, China2Research center on Flood & Drought Disaster Reduction of the Ministry of Water Resources,

China Institute of Water Resources and Hydropower Research, Beijing, China3College of Hydrology and Water Resources, Hohai University, Nanjing, China

Correspondence: Zikang Xing (xzk@hhu.edu.cn)

Published: 16 September 2020

Abstract. Drought intensity and frequency are increasing in recent years in multiple regions across the worlddue to global climate change and consequently drought forecasting research has received more and more atten-tion. Previous studies on drought forecasting mostly focus on meteorological drought based on precipitation andtemperature. However, the trend of predicting agriculture and hydrological drought, which consider soil moistureand runoff, have developed rapidly in recent years. Hydrological drought forecasting is based on the hydrolog-ical models and the model structure plays a role to improve predictions. This study scrutinized more than 50hydrological models, including lumped models, semi-distributed models, distributed models, surface water andgroundwater coupled models, to explore the adaptability of hydrological models in drought simulation and fore-casting. The advantages and disadvantages of typical models, such as DTVGM, GWAVA, and HEC-HMS modelswere analyzed to provide valuable reference for drought forecasting model development. Future work aims atimproving the hydrological models to simulate the drought processes and make better prediction.

1 Introduction

Drought intensity and frequency are increasing in past andrecent years in multiple across the globe due to global climatechange (Wilhite and Glantz, 1985). In this context, meth-ods to predict drought has received more and more atten-tion (Edwards and McKee, 1997). Previous study of droughtforecasting mostly focused on meteorological drought basedon precipitation and temperature, while the trend predic-tion of agriculture and hydrological drought, which considersoil moisture and runoff, have developed rapidly in recentyears (Wilhite, 2000; Wanders et al., 2019). There are twomain types of methods involved in the hydrological droughtforecasting. One is the statistical method that tries to de-velop construct the relationship between hydrological char-acteristics and drought events, such as the gray forecastingmethod (Vishnu and Syamala, 2012), Markov chain method(Paulo and Pereira, 2007), Error back Propagation neural net-

work (Raju et al., 2011), and correlation analysis. The sec-ond method is the methods based on hydrological modelsand coupled atmospheric-hydrological models (Mishra andSingh, 2011). For the latter method, the model structure playsa significant role to improve predictions.

Most hydrological models have been developed for floodsimulation and prediction (Huggins and Monke, 1970). Gen-erally, flood generation tends to focus on fast processes andpeaks can form in a few days or even hours, while the pro-cess of drought development is much slower covering sev-eral months or years. Therefore, flood forecasting is a short-term high flow prediction, but the drought forecasting fo-cuses on medium and long-term low flow prediction (Mishraand Singh, 2010). Most hydrological models could improveon drought prediction in humid watersheds as they put em-phasis on peak flow simulation rather than low flow (Yu etal., 1999). If these models are used for the drought forecast-ing, they might suffer from the limitations of structure. Two

Published by Copernicus Publications on behalf of the International Association of Hydrological Sciences.

262 Z. Xing et al.: A review of the adaptability of hydrological models for drought forecasting

scientific questions are addressed: what are the limitations ofexisting hydrological models when used for the drought fore-casting, and how to improve the structure in order to makethe drought prediction better? In this study, we scrutinizedmore than 50 hydrological models, including lumped mod-els, semi-distributed models, distributed models, integratedsurface water and groundwater models, to explore the adapt-ability of hydrological models in drought simulation andforecasting. Afterwards, improvements of the model struc-ture are proposed.

2 Methods

2.1 Model selection and classification

More than 50 hydrological models were involved in thisstudy. The main source was from the model review paperby Singh and Woolhiser (2002), some seldom used modelswere abandoned, and other recent representative hydrolog-ical models were also included (20 models). The baselineof model selection is that the model has been widely usedand is easy to get the manual. According to the evolution ofhydrological models, these selected models were classifiedinto four types: lumped model, semi-distributed model, dis-tributed model and integrated surface water and groundwa-ter model. The selected models include: 13 lumped models(Fig. 1), 6 semi-distributed models (Fig. 2), 29 distributedmodels (Fig. 3) and 10 integrated surface water and ground-water models (Fig. 4).

2.2 Evaluation method for assessment of theadaptability of hydrological models for droughtforecasting

2.2.1 Evaluation criteria

Considering the differences between flood and drought fore-casting, their corresponding model structure need to be dis-tinct. For drought forecasting, emphasis on low flows, there-fore, the simulation of evapotranspiration, soil water mois-ture and the recession process need to be well developed.Snow melting, vegetation interception, groundwater and sur-face water exchange cannot be neglect any more. The influ-ences of crops and soil water dynamics should be consid-ered in the low flow simulation and prediction. In addition,human impacts, including water storage and drainage fromreservoirs, water transfer, agricultural irrigation, groundwa-ter pumping or artificial recharging, water consumption, alsoneed to be included in drought forecasting, because they havesignificant effect on drought in some areas (Van Loon et al.,2016). Given that the drought forecasting needs longer leadtimes for prediction, hydrological models should be linkeddirectly to the climate forecasting results in order to extendthe lead times. Since drought forecasting deals with low flow,the energy balance should be considered to a certain extentto supplement the water balance calculation. To sum up, 15

Table 1. Summary of evaluation indicators.

No. Evaluation indicators

1 Special human impact module2 Water storage and drainage from reservoirs3 Water transfer4 Irrigation simulation5 Groundwater pumping and artificial recharging6 Water consumption7 Evapotranspiration simulation8 Canopy interception9 Snowmelt simulation10 Soil water moisture simulation11 Low flow recession process12 Surface water and groundwater exchange13 Connection to climate forecasts14 Energy balance15 Crop growth interaction with soil moisture

evaluation criteria (Table 1) were used to explore the adapt-ability of hydrological models for drought forecasting in thisstudy.

2.2.2 Evaluation method

A rank evaluation method was used in this study. Threegrades were distinguished: 0, 1 and 2. “0” stands for no con-sideration of the function or module; “1” stands for simplecalculation of the function or module; “2” stands for matureor powerful calculation of the function or module.

3 Results

3.1 Lumped model evaluation

The adaptability of lumped hydrological models for droughtforecasting is shown in Fig. 1. Most of selected lumpedmodels simulate evaporation calculation except CLS model,whereas the XAJ and VM show the powerful function with athree layers evaporation calculation method. 70 % of the se-lected models simulate soil water moisture with simple equa-tions, while the Sacramento model divides the soil into differ-ent layers and calculate soil moisture in each layer. Five mod-els include simulation of canopy interception and snowmelt.Three models (i.e. EPIC, ARM and SVAT) consider the en-ergy balance together with the water balance. Only the EPICmodel has irrigation module, while the EPIC and ARM con-sider the influences of crop growth.

3.2 Semi-distributed model evaluation

The evaluation results of six selected semi-distributed mod-els are shown in Fig. 2. Results exhibit that all the selectedsemi-distributed models simulate evaporation and soil water

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Z. Xing et al.: A review of the adaptability of hydrological models for drought forecasting 263

Figure 1. Evaluation of the adaptability of lumped hydrological models for drought forecasting. Where white color stands for grade 0 (noconsideration of the function or module); gray color stands for grade 1 (simple simulation of the function or module); black color stands forgrade 2 (powerful simulation of the function or module).

moisture, whereas the LASCAM and ARNO appear pow-erful soil water moisture simulation. The ARNO model in-volves the spatial probability distribution of soil moistureto dynamically change the saturation contribution area. TheSWRRB and SLURP consider the effects of human activi-ties, such as water storage and drainage from reservoirs. Inparticular, the SLURP model includes simulation of severalhuman activities, including water transfers, irrigation andgroundwater pumping and artificial recharging. The ARNOmodel simulates water consumption, while the Top modeltakes the exchange of groundwater and surface water intoconsideration. All semi-distributed models only simulate wa-ter balance without taking the energy balance into account.None of the selected models consider low flow recession andcrop growth influences on soil water moisture and evapotran-spiration.

3.3 Distributed model evaluation

The evaluation results of the 29 selected distributed mod-els are shown in Fig. 3. All the models simulate evapo-transpiration and soil water moisture, where SWAT, WIS-TOO, CASC2D, PARCHED-THIRST, VIC and PRMS ap-proach the soil water moisture simulation in different ways.SWAT, GWAVA, MIKE-SHE and DTVGM consider mostof the human activities that impact the hydrological sys-tem. The four human activity modules we put forward, areranked as follows: water storage and drainage from reser-voirs, water transfer, irrigation, groundwater pumping and

artificial recharging, water consumption. The impact of thereservoirs is most frequently addressed by model developers.Nearly half of the selected models consider canopy intercep-tion and snowmelt modules, which often can be explainedfor which catchment the model originally has been devel-oped. Half of selected models consider groundwater and sur-face water exchange, among which SWIM, SHETRAN andHEC-HMS containing specialized groundwater simulationmodules. Five models consider the simulation of low flowconditions, while night models (i.e. HYDROTEL, CREST,HSPF, GWAVA, VIC, Wasim-ETH, MIKE-SHE, DHSVMand GBHM) can be connected to weather forecasts well, be-cause of their grid-based structure. Four models (i.e. SWAT,PARCHED-THIRST, SWIM, and Mike-SHE) investigatecrop growth influences on the hydrological system. Com-pared with lumped and semi-distributed models, many dis-tributed models start to consider the energy balance to sup-plement the water balance simulation.

3.4 Integrated surface water and groundwater modelevaluation

The evaluation results of 10 selected integrated surface waterand groundwater models are shown in Fig. 4. All the modelstudied consider evaporation, canopy interception, soil wa-ter moisture and the exchange between surface water andgroundwater. The ability to simulate groundwater flow andgroundwater pumping and artificial recharging makes thistype of models more powerful than the other types of models.

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264 Z. Xing et al.: A review of the adaptability of hydrological models for drought forecasting

Figure 2. Evaluation of the adaptability of semi-distributed hydrological models for drought forecasting. Where white color stands for grade0 (no consideration of the function or module); gray color stands for grade 1 (simple simulation of the function or module); black colorstands for grade 2 (powerful simulation of the function or module).

Figure 3. Evaluation of the adaptability of distributed hydrological models for drought forecasting. Where white color stands for grade 0(no consideration of the function or module); gray color stands for grade 1 (simple simulation of the function or module); black color standsfor grade 2 (powerful simulation of the function or module).

MODHMS, HydroGeoSphere and Parflow are fully coupledmodels of groundwater and surface water. They use partialdifferential equations to describe surface water and ground-water flow processes. SWATMOD, and MODHMS performwell in simulating human activities. The Parflow model is ahydrological model for parallel computing that takes the en-

ergy balance into account and can be efficiently linked to cli-mate models. The SWATMOD as the coupled model betweenSWAT and Modflow consider the influence of crop growth onthe hydrological system.

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Figure 4. Evaluation of the adaptability of integrated surface water and groundwater models for drought forecasting. Where white colorstands for grade 0 (no consideration of the function or module); gray color stands for grade 1 (simple simulation of the function or module);black color stands for grade 2 (powerful simulation of the function or module).

4 Discussion

The model structure of lumped hydrological model seemsa bit simpler compared with the other types of models,and they seldom consider human impact (Bergstrom, 1995).While distributed models investigate more human impactin the hydrological cycle, such as the water storage anddrainage from reservoirs, water transferring, water consump-tion, irrigation. The integrated surface water and ground-water model couple the advantages of surface water andgroundwater simulations. They consider the exchange be-tween surface water and groundwater, and enable to simulatethe groundwater pumping and artificial recharging. However,they are too sophisticated to be used for drought forecast-ing, because they need too many data to run (Beven and Bin-ley, 1992). In summary, distributed models are more suitablefor drought forecasting compared with lumped and semi-distributed models. Results indicate that SWAT, GWAVA,MIKE-SHE and DTVGM are the most powerful in the cate-gory of the distributed models because they simulate the hu-man impact on the hydrological system, and they solve theenergy balance together with water balance.

The MIKE-SHE model covers ranges of physical pro-cesses with high requirements on parameters and data, andhence its operation seems more sophisticated than the otherthree above-mentioned distributed models (Refsgaard andStorm, 1995). The SWAT model is an open source modeland it is updated by world researchers, which have developedseveral modules for human impacts and crop growth. TheSWAT model has been widely used in non-point source pol-

lution simulation (Jayakrishnan et al., 2005), but seldom hasbeen used for drought forecasting. When applied to droughtforecasting, it is better to improve the low flow simulationsand the connection to climate forecasting. The advantage ofGWAVA model is the human impact module that can simu-late water demand, water transfer, agricultural irrigation andpopulation distribution as a driver for human activities. How-ever, the simulation modules for human impacts seems a bitsimple. In contrast, the DTVGM model was developed basedon the characteristics of Chinese Yellow River basin, withemphasis on water conservation, water consumption, reser-voirs and low flow simulations (Ning et al., 2016). The high-light of HEC-HMS is reflected in the flexibility of its modelstructure, which can be adapted to the catchments for dif-ferent natural conditions (Hydrologic Engineering Center,2000). To sum up, combination of the model structures ofSWAT, GWAVA and DTVGM might be a good solution fordrought forecasting, using the flexible structure of the HEC-HMS model.

5 Conclusions

This study scrutinized more than 50 hydrological models, in-cluding lumped models, semi-distributed models, distributedmodels, surface water and groundwater coupled models, toexplore the adaptability of hydrological models for droughtsimulation and forecasting. In this paper, we discuss the lim-itations of the wide range of selected hydrological modelsto be used for the drought forecasting and to propose im-provement of model structures to make better fit for drought

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266 Z. Xing et al.: A review of the adaptability of hydrological models for drought forecasting

prediction. Results indicate that distributed models are moresuitable for drought forecasting compared with the othertypes of models. A combination of SWAT, GWAVA andDTVGM might be a good solution for drought forecastingusing the flexible structure of the HEC-HMS model.

Data availability. All relevant data are within the paper.

Author contributions. PY and WS designed the research; ZS andJL collected the data; ZX and MM analyzed the data and wrote thepaper.

Competing interests. The authors declare that they have no con-flict of interest.

Special issue statement. This article is part of the special issue“Hydrological processes and water security in a changing world”.It is a result of the 8th Global FRIEND–Water Conference: Hydro-logical Processes and Water Security in a Changing World, Beijing,China, 6–9 November 2018.

Financial support. This research has been supported bythe IWHR Research & Development Support Program (grantno. JZ0145B582017), the the National Natural Science Founda-tion of China (grant no. 51609257), the the Hydraulic scienceand technology in Hunan Province (grant no. [2017]230-36),and the the National Key R&D Program of China (grantno. 2017YFC1502406).

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Proc. IAHS, 383, 261–266, 2020 https://doi.org/10.5194/piahs-383-261-2020

https://doi.org/10.1155/2011/686258https://doi.org/10.1038/ngeo2646https://doaj.org/article/806ab2d8b3134e98a512ddf3409ca26fhttps://doaj.org/article/806ab2d8b3134e98a512ddf3409ca26fhttps://doi.org/10.1175/JHM-D-18-0040.1

AbstractIntroductionMethodsModel selection and classificationEvaluation method for assessment of the adaptability of hydrological models for drought forecastingEvaluation criteriaEvaluation method

ResultsLumped model evaluationSemi-distributed model evaluationDistributed model evaluationIntegrated surface water and groundwater model evaluation

DiscussionConclusionsData availabilityAuthor contributionsCompeting interestsSpecial issue statementFinancial supportReferences