Elements Of Water Cycle Research Articles

Evaluation of the fully coupled WRF and WRF-Hydro modelling system initiated with satellite-based soil moisture data

ABSTRACT This study comparatively evaluates the skill of the (un)coupled Weather Research and Forecasting (WRF) – WRF-Hydro system supported with satellite-based soil moisture initiation in long-term simulations of hydrometeorological variables under humid and semi-arid climate conditions. Prior to the coupling, the WRF-Hydro model is calibrated using streamflow data at different data scales (i.e. hourly and daily) to discuss the influences of the changing temporal resolution of the reference dataset on the optimum parameter values. According to the results, fully coupled models correct the location and magnitude of the occurrence of hourly extreme precipitation. Changing the initial soil moisture data source affects the terrestrial water cycle elements in the semi-arid region (i.e. Mediterranean (MED)) more than in the humid area (i.e. Eastern Black Sea (EBS)), especially in spring and summer. The initiation of the coupled model with satellite-based soil moisture improves the streamflow outputs after a reasonable spin-up period for the MED region.

Study on Response Process and Time Delay Effect of Groundwater Dynamic in Northeastern Margin of Tibetan Plateau

Under the background of drastic global climate change, the evolution law of groundwater resources in the northeastern margin of the Tibetan Plateau presents new characteristics, and the groundwater is gradually becoming more complicated, diversified and disordered. In this study, cross-correlation analysis, wavelet analysis and cross-wavelet transform were used to explore the response mechanism and time delay effect of groundwater, exploitation amount, rainfall and surface runoff in the northeastern margin of the Tibetan Plateau. The results show that the groundwater depth increased with the increase in the exploitation amount and decreased with the increase in the rainfall-to-exploitation ration and the surface runoff-to-exploitation ratio from 1980 to 2020. On the annual scale, groundwater, rainfall and surface runoff had a strong cohesiveness period of 12a. On the monthly scale, groundwater lagged behind rainfall and surface runoff for 3 months and 2 months, respectively. The above conclusions provide a scientific theoretical basis for deepening the characteristics of groundwater endowment, the evolution law of water cycle elements and the theory of the hydrological cycle in the northeastern margin of the Tibetan Plateau.

Development and Application of An Integrated Urban Water Cycle System by Combining Water Cycle Elements

Smart city in water resources area attempts are being made by establishing an integrated urban water cycle model for a stable water supply and efficient water management in the city. Accordingly, the need for simulation and integrated management of water consumption in cities is increasing. If it is possible to predict and respond in advance to consumers' water consumption, more efficient urban water resource management will be possible based on river intake. Therefore, in this study, an integrated urban water cycle model was constructed that links river intake, water purification plants, retention tanks, water distribution, sewage pipe networks, sewage treatment plants, and river discharge of treated water. It was developed using C++, and was built by linking the modules of the water intake pump station, retention tank, water purification plant, sewage treatment plant, water supply pipe network, and the sewage pipe network. Among them, the water intake pumping station and retention tank were developed independently, and the other modules were linked with commercial software such as WaterFlow, MassFlow, EPANET, and SWMM. The model measures data such as water quality factors and flow rates for each module, displays the operation status, and enables linkage for each module, even when the measurement time interval is different. In addition, warnings and error messages were generated when a problem occurred during the operation of each module. To verify the applicability of the developed integrated model, the change in the water level of the retention tank was calculated by simulating consumer water consumption. As a result, it was confirmed that the water level change in the retention tank was proper, which meant that the operation changed from the intake pumping station. The developed model is expected to be used as an integrated urban water cycle model in the future.

Framework for Healthiness Assessment of Water Cycle to Decide the Priority of Enhancement and Restoration Plans

The water cycle in watersheds is vulnerable due to climate change; hence, the need for sustainable watershed management is increasing. This paper suggests a framework for a healthiness assessment of the water cycle to provide a guideline for systematic watershed management considering the previous and current states. The suggested framework aims to prioritize restoration and enhancement plans based on the graded healthiness of the water cycle elements by the watersheds. The framework is composed of two assessment procedures: a problem-focused assessment to identify problems such as flood, drought, and river depletion in the watershed and the highest priority assessment to select the watershed for enhancement and restoration plans. The healthiness assessment method for each metric is suggested based on the Korean Framework Act on Water Management. The framework was applied to four different watersheds in South Korea. The framework is proven to be an effective method to identify practical emerging problems for the water cycle in each watershed. The framework can contribute to providing technical information to detect the water problem of the watershed by objectively diagnosing the watersheds with various potential water problems via the healthiness assessment.

A composite index coupling five key elements of water cycle for drought analysis in Pearl River basin, China

Drought, as a natural disaster, has widespread consequences and is notoriously difficult to manage. Critical to developing a drought management strategy is the identification and assessment of drought. To that end, this study developed a new composite index, called the standardized water cycle index (SWCI) based on the water cycle and water balance. The SWCI couplesd the key elements of the water cycle, including precipitation, evapotranspiration, leaf area index, surface runoff, and subsurface runoff, and requires the joint distribution of these elements which was determined using the D-vine copula. The Kendall transform was used to reduce the dimensionality of the five-element joint probability density function, which was then inversed to obtain the SWCI which was then evaluated with the data from the Pearl River basin obtained using the CMIP6. Results showed that the SWCI satisfactorily evaluated drought conditions, while reflecting the drought-mitigating effect of vegetation and subsurface runoff. The SWCI was also able to evaluate drought in areas with a high level of human activity.

Assessment of Water Cycle in Agricultural Watershed Based on Canal Network Modeling

Recently, various factors such as climate change, watershed environment change, and, socio-economic change, have been shown to have a major impact on the hydrological water cycle and on available water resources in agricultural watersheds. Therefore, it is necessary to identify the water cycle elements of watersheds accurately and to quantify them objectively. Agricultural watersheds can be divided into the basin, irrigation facilities such as reservoir and pumping stations, irrigation areas, and water cycle elements such as rainfall and evapotranspiration water supply and demand. A systematic management system of agricultural water cycle should be established through element analysis, module development, and modeling techniques for comprehensive interpretation of agricultural watersheds. This study involved the monitoring and modeling of inlet, outlet, and reservoir to analyze and quantify water cycle elements in the Madun reservoir (located in Anseong, Gyeonggi-do) and Heungeop reservoir (located in Wonju, Gangwon-do). The watershed runoff, water supply and drainage of irrigation canal, and return flow were estimated using the Storm Water Management Model (SWMM) based on analysis of canal networks and hydraulic calculations. These results can be utilized to ensure stable supply of agricultural water resources and to inform water management policies.

Evolutionary trend of water cycle in Beichuan River Basin of China under the influence of vegetation restoration

To understand the influence of vegetation restoration on the water cycle in semiarid areas, the effects of vegetation restoration on evolution of the key elements of water cycle were clarified by analyzing the evolutionary trend of atmospheric precipitation, ecological consumption water, and surface runoff on a river basin scale on the basis of analytical results of the changes in vegetation coverage and the long-term meteorological and hydrological monitoring data of Beichuan River Basin. The results show that the vegetation cover in the Beichuan River basin has rapidly increased in the hilly and mountainous areas since the 1980s, especially from 2000 to 2019, with the maximum and average vegetation cover rates increased by 14.98% and 52.2%, respectively. During 1956-2016, the annual precipitation in the basin remained relatively stable; the annual surface runoff slightly declined, with an average attenuation rate of 20 million m3/10a. The main reason for the runoff decline is the increase in ecological water induced by the vegetation restoration, which has changed the spatial-temporal distribution of the water from atmospheric precipitation in the basin. Spatially, more precipitation was converted into ecological water. As a result, the remnant runoff supplied to the lower reaches reduced accordingly. Temporally, more precipitation participated in the soil water - groundwater cycle, thus prolonging the outward drainage period of the precipitation. Moreover, the large-scale vegetation restoration induced a significant decrease in the surface wind speed, evaporation from water surface and drought index. As a result, a virtuously mutual feedback relationship was formed between the vegetation and meteorological elements. Therefore, vegetation restoration is of great significance for the improvement in the water conservation capacity and semiarid climate conditions in the Beichuan River basin.

An Evaluation Study of the Fully Coupled WRF/WRF-Hydro Modeling System for Simulation of Storm Events with Different Rainfall Evenness in Space and Time

With the aim of improving the understanding of water exchanges in medium-scale catchments of northern China, the spatiotemporal characteristics of rainfall and several key water cycle elements e.g., soil moisture, evapotranspiration and generated runoff, were investigated using a fully coupled atmospheric-hydrologic modeling system by integrating the Weather Research and Forecasting model (WRF) and its terrestrial hydrologic component WRF-Hydro (referred to as the fully coupled WRF/WRF-Hydro). The stand-alone WRF model (referred to as WRF-only) is also used as a comparison with the fully coupled system, which was expected to produce more realistic simulations, especially rainfall, by allowing the redistribution of surface and subsurface water across the land surface. Six storm events were sorted by different spatial and temporal distribution types, and categorical and continuous indices were used to distinguish the applicability in space and time between WRF-only and the fully coupled WRF/WRF-Hydro. The temporal indices showed that the coupled WRF-Hydro could improve the time homogeneous precipitation, but for the time inhomogeneous precipitation, it might produce a larger false alarm than WRF-only, especially for the flash storm that occurred in July, 2012. The spatial indices showed a lower mean bias error in the coupled system, and presented an enhanced simulation of both space homogeneous and inhomogeneous storm events than WRF-only. In comparison with WRF-only, the fully coupled WRF/WRF-Hydro had a closer to the observations particularly in and around the storm centers. The redistributions fluctuation of spatial precipitation in the fully coupled system was highly correlated with soil moisture, and a low initial soil moisture could lead to a large spatial fluctuated range. Generally, the fully coupled system produced slightly less runoff than WRF-only, but more frequent infiltration and larger soil moisture. While terrestrial hydrologic elements differed with relatively small amounts in the average of the two catchments between WRF-only and the fully coupled WRF/WRF-Hydro, the spatial distribution of elements in the water cycle before and after coupling with WRF-Hydro was not consistent. The soil moisture, runoff and precipitation in the fully coupled system had a similar spatial trend, but evapotranspiration did not always display the same.

Drought Monitoring of Southwestern China Using Insufficient GRACE Data for the Long-Term Mean Reference Frame under Global Change

Global changes, such as human activities and climate change, increase the odds of worsening drought. The Gravity Recovery and Climate Experiment (GRACE) satellite provides an opportunity to monitor drought levels by the total amount of water, instead of using a small finite set of water cycle elements or indirect indicators. The potential gap lies in the insufficient size of the GRACE record. The database does not meet the requirements of a stationary annual cycle calculated over a relatively long period as recommended by the IPCC, and the disturbance from long-term global changes is often not considered. In this work, a GRACE-based modulated water deficit (GRACE-MWD) process for drought monitoring under the modulated annual cycle (MAC) reference frame in southwest China was proposed. GRACE-MWD achieved a higher ratio of agreement with the standardized precipitation evapotranspiration index at a time scale of 3 months (SPEI03): it ranged from 0.48 to 0.84, while the GRACE-based drought severity index (GRACE-DSI) ranged from 0.48 to 0.68. Compared with remote sensing datasets widely used in drought monitoring, GRACE-MWD data are less affected by seasonality from land-cover categories, which benefit from the MAC reference frame. The ratio-of-agreement metric for the study area showed that GRACE-MWD had a time scale between 7 and 11 months in reference to SPEI and the standardized precipitation index (SPI). The stability of the MAC reference frame to GRACE-MWD was further discussed when GRACE records were extended and was more stable than that of the stationary annual cycle. GRACE-MWD meets global changes via an adaptive reference frame, which is worthy of generalizing to global applications.

Isotopic analysis of water cycle elements in different land covers in a small headwater watershed

In this study, comparisons of isotopic variation of rainfall, throughfall, surface water, and groundwater were conducted in the Meilin watershed, which represents two different land uses, chestnut wood and bamboo. Also, isotopic differences between rainfall and throughfall were identified in these sub-watersheds. The results showed that the isotopic value of incremental rainfall, incremental throughfall and surface water exhibited a marked temporal variation in the selected sub-watersheds. The throughfall isotopic variation range was smaller than that of rainfall, which may result from the different production process between rainfall and throughfall. However, the isotopic composition difference between rainfall and throughfall resulting from different land uses was insignificant. The range of isotopic composition variation of surface water was not the same as that of rainfall, indicating that surface water came from a mix of precipitation and water stored before the rainfall event. The temporal variation of the isotopic composition of groundwater was small, implying that the influence of different land uses on groundwater isotopic composition was insignificant. The total variation range of δ2H and δ18O of groundwater was smaller than that of surface water and sequential incremental rainfall, which means the δ18O of groundwater can be replaced by that of base flow before the event in the hydrograph separation.

Signal of Acceleration and Physical Mechanism of Water Cycle in Xinjiang, China.

Global warming accelerates water cycle with features of regional difference. However, little is known about the physical mechanism behind the phenomenon. To reveal the links between water cycle and climatic environment, we analyzed the changes of water cycle elements and their relationships with climatic and environmental factors. We found that when global warming was significant during the period of 1986-2003, the precipitation in Tarim mountains as well as Xinjiang increased rapidly except for Tarim plains, which indicated that there existed a signal of acceleration for water cycle in Xinjiang. The speed of water cycle is mainly affected by altitude, latitude, longitude, slope direction, and the most fundamental element is temperature. Moreover, according to Clausius-Kela Bai Lung relation, we found that the climate change induced the increase of temperature and accelerated the local water cycle only for the wet places. Our results provide a possible physical mechanisms of water cycle and thus well link the climate change to water circulation.

Time series analysis of reference crop evapotranspiration for Bokaro District, Jharkhand, India

AbstractEvapotranspiration is the one of the major role playing element in water cycle. More accurate measurement and forecasting of Evapotranspiration would enable more efficient water resources management. This study, is therefore, particularly focused on evapotranspiration modelling and forecasting, since forecasting would provide better information for optimal water resources management. There are numerous techniques of evapotranspiration forecasting that include autoregressive (AR) and moving average (MA), autoregressive moving average (ARMA), autoregressive integrated moving average (ARIMA), Thomas Feiring, etc. Out of these models ARIMA model has been found to be more suitable for analysis and forecasting of hydrological events. Therefore, in this study ARIMA models have been used for forecasting of mean monthly reference crop evapotranspiration by stochastic analysis. The data series of 102 years i.e. 1224 months of Bokaro District were used for analysis and forecasting. Different order of ARIMA model was selected on the basis of autocorrelation function (ACF) and partial autocorrelation (PACF) of data series. Maximum likelihood method was used for determining the parameters of the models. To see the statistical parameter of model, best fitted model is ARIMA (0, 1, 4) (0, 1, 1)12.

Spatiotemporal characteristics and water budget of water cycle elements in different seasons in northeast China**Project supported by the State Key Development Program for Basic Research of China (Grant Nos. 2013CB430204 and 2012CB955902) and the National Natural Science Foundation of China (Grant Nos. 41175067, 41175084, and 41205040).

In this paper, we study the spatiotemporal characteristics of precipitable water, precipitation, evaporation, and water–vapor flux divergence in different seasons over northeast China and the water balance of that area. The data used in this paper is provided by the European Center for Medium-Range Weather Forecasts (ECMWF). The results show that the spatial distributions of precipitable water, precipitation, and evaporation feature that the values of elements above in the southeastern area are larger than those in the northwestern area; in summer, much precipitation and evaporation occur in the Changbai Mountain region as a strong moisture convergence region; in spring and autumn, moisture divergence dominates the northeast of China; in winter, the moisture divergence and convergence are weak in this area. From 1979 to 2010, the total precipitation of summer and autumn in northeast China decreased significantly; especially from 1999 to 2010, the summer precipitation always demonstrated negative anomaly. Additionally, other elements in different seasons changed in a truly imperceptible way. In spring, the evaporation exceeded the precipitation in northeast China; in summer, the precipitation was more prominent; in autumn and winter, precipitation played a more dominating role than the evaporation in the northern part of northeast China, while the evaporation exceeded the precipitation in the southern part.The Interim ECMWF Re-Analysis (ERA-Interim) data have properly described the water balance of different seasons in northeast China. Based on ERA-Interim data, the moisture sinks computed through moisture convergence and moisture local variation are quite consistent with those computed through precipitation and evaporation, which proves that ERA-Interim data can be used in the research of water balance in northeast China. On a seasonal scale, the moisture convergence has a greater influence than the local moisture variation on a moisture sink, and the latter is variable slightly, generally as a constant. Likewise, in different seasons, the total precipitation has a much greater influence than the evaporation on the moisture sink.

The characteristics of the summer atmospheric water cycle over China and comparison of ERA-Interim and MERRA reanalysis

Atmospheric water cycle process includes precipitation, evaporation, water vapor transport and other links. The temporal and spatial characteristics of the atmospheric water cycle over China in summer are investigated by using the ERA-Interim and MERRA reanalysis from 1979 to 2012. Comparison and performance analyses of these two reanalysis data are given. The obtained results are as follows. 1) the spatial distributions of precipitation, evaporation and precipitable water are highly similar to each other, and all gradually decrease from southeast coast to northwest inland regions. Because the differences in physical condition, precipitation and evaporation among different underlying surfaces, mutually promot or mutually restrict each other, the interactions among them have positive and negative feedback mechanisms. Precipitable water mainly concentrates in the ground to the 700 hPa height, accounts for about 75% of the total quantity. 2) All of the atmospheric water cycle elements have obvious characteristics of climate change, especially in these areas like Northwest China, Tibet and Northeast China. The zonal flux of water vapor transport significantly decreases in most parts of the northern, while the meridional flux of water vapor transport significantly increases in the northern region of Northwest China. 3)The reproduction ability to change characteristics of precipitation is better than that of evaporation based on these reanalyses. The temporal and spatial distribution characteristics of moisture transport situation and the various levels of atmospheric water vapor content are highly consistent with each other. The simulations of flux climate change trend of precipitation and water vapor transport are more accurate and more reliable. 4) Interim reanalysis is applicable to the study of the southwest, Southeast and northeast regional atmospheric water balance, water cycle elements can maintain balance well, while MERRA reanalysis is more reasonable in Southwest and northwest.

The Megha‐Tropiques mission: day 1 algorithms

The Megha-Tropiques mission is a mission jointly built by the Centre National d'Études Spatiales and the Indian Space Research Organisation launched in October 2011. ‘Megha’ means cloud in Sanskrit and ‘Tropiques’ is the French word for tropics. The major innovation of Megha-Tropiques is to bring together a suite of complementary instruments on a dedicated orbit that strongly improves the sampling of the water cycle elements. Indeed, the low inclination on the equator (20°) combined with the elevated height of the orbit (867 km) provides unique observing capabilities with up to 6 over-passes per day for the best case. The following payloads are embarked on board: SCARAB, a wide band instrument for inferring longwave and shortwave outgoing fluxes at the top of the atmosphere (cross track scanning, ∼ 40 km resolution at nadir); SAPHIR, a microwave sounder for water vapour sounding: six channels in the WV absorption band at 183.31 GHz (cross track, resolution ∼ 10 km); MADRAS, a microwave imager for precipitation: channels at 18, 23, 37, 89 and 157 GHz, H and V polarisations (conical swath, resolution <10 km to 40 km). A fourth instrument, a GPS-ROSA receiver, completes the mission. The scientific objectives of the mission deal with the water and energy cycle in the intertropical region. To achieve these objectives, a suite of algorithms has been developed based on the mission payloads and the available ancillary observations. This Special Issue presents the day 1 Megha-Tropiques retrievals and approaches with the emphasis on the quantification of the uncertainties associated with the products. The first series of papers by Brogniez et al., Aires et al. and Bernado et al. showcase the importance of the microwave payloads combination of SAPHIR and MADRAS for the estimation of the humidity profile. The instantaneous retrieval of surface rainfall is shown to be improved by using a renewed rainfall detection scheme (Kacimi et al.) and the uncertainty associated with the Bayesian approach to the estimation of the surface rain flux has been quantified over West Africa by Kirstetter et al. The integrated products that are envisioned for the scientific exploitation of the mission concern the accumulated daily rain amount and the composite life cycle of mesoscale convective systems. In both cases, the MT data are combined with the infrared geostationary imagery. Fiolleau and Roca, using the TRMM data as a surrogate, propose a first tropical wide composite of the rainfall evolution during the life cycle of convective systems and underline the improvement in sampling brought by the Megha-Tropiques mission. Chambon et al. show that the main source of uncertainty for the daily rain amount lies in the intermediate estimates of the instantaneous rain rates and promote a fully developed error model that includes the calibration, sampling and algorithm terms. Specific methodological developments for the validation of such products are summarized by Gosset et al., who emphasize the need for integrated hydrological validation in complement of the rainfall evaluation. While the Special Issue is mainly directed towards presenting the French team developments, a final paper by Gohil et al., highlights the Indian algorithms scenario. This Special Issue of Quarterly Journal of the Royal Meteorological Society brings to the future users of the MT data and products a suite of reference papers that should be useful for their further scientific investigations.

Changes in some elements of the water cycle in the easternmost part of the Baltic Sea Drainage Basin between 1945 and 2010

Soil moisture and evaporation are the most important elements of the terrestrial water cycle. In situ data from 14 stations with soil moisture observations, 13 stations with pan evaporation and 200 stations with precipitation measurements are used to analyse temporal changes in these elements of the terrestrial water cycle over the Russian part of the Baltic Sea Drainage Basin.It was determined that soil moisture, pan evaporation and visible evaporation have exhibited significant changes during the past 45 years. These changes reflect the non-uniform character of moistening changes over the Russian part of the Baltic Sea region.

Necessity and feasibility for an ET-based modern water resources management strategy: A case study of soil water resources in the Yellow River Basin

The necessity and feasibility of an ET-based modern water resources management was analyzed to improve assessment of critical water resources scarcity in the region/basin. This analysis was based on the whole water cycle process and its analysis object is evapotranspiration (ET), a main consumption component in the water resources dynamic transformation process. A case study was undertaken by selecting soil water resources in the Yellow River Basin and employing the WEP-L distributed hydrological model with physics mechanisms. This paper discusses the amount and consumption efficiency of soil-water resources according to completely simulated results of water cycle elements throughout the basin. Results indicate that it is important for the ET-based modern water resources management strategy to alleviate water resources scarcity because it may not only avoid unused water wasting but also improve water use efficiency. Therefore, an ET-based modern water resources management scheme is a good complement to the traditional water resources demand management system.

Geographical overview of water balance of Slovenia 1971–2000 by main river basins

T his overview of the hydrogeographical characteristics of the Slovenian water balance 1971–2000 reviews three main water cycle elements: precipitation, evapotranspiration and runoff. Results show their spatial distribution and strong interdependency in by main river basins of Slovenia. Greatest amounts of water are in the Soca river basin and the smallest in the Slovenian part of the Mura river basin. Average yearly quantities of water in Slovenia for the period 1971–2000 are: precipitation 1579 mm, evapotranspiration 717 mm and runoff 862 mm. Compared with the water quantities data of 1961–1990 period, the precipitation is in same rank, the evapotranspiration increased and the runoff decreased. Despite being a “wet” country by world standards, available water resources in Slovenia are declining.

Study on evaporation of bielahong river basin

The Bielahong River is a typical marsh river whose hydrological characteristics the hydrological characteristics that of the whole Sanjiang Plain. Evaporation is an important element in water cycle which demonstrates water output. The paper gives the annual evaporation of the basin; calculates the evaporation coefficient in summer and the coefficient between marsh evaporation and pure water evaporation; analyses the ratios of evaporation to precipitation and to runoff; at last the paper reaches a conclusion that in years with different precipitation the effects of marsh on runoff are different.