Water Storage Effect Research Articles

Study on valley deformation of high arch dams based on nonlinear rheological damage model

The scale of the high arch dam project is large, and the water level is high. The construction and water storage effect will significantly impact the rock mass of the high slopes on both sides, especially on the structural planes such as internal faults. Based on the Jinping Ⅰ high arch dam, an improved Nishihara rheological damage model was established to address the phenomenon of valley shrinkage deformation. The stress and deformation states of the rock mass and dam in the reservoir area were calculated, and the results were compared with the conventional elastic–plastic finite element method. The results indicate that the improved parallel Nishihara rheological damage model can better conform to the deformation properties of the internal structural planes of the rock mass, and the calculation results using this model are closer to the actual deformation situation. When considering the structural plane's rheological characteristics, the valley shrinkage deformation law is consistent with the conventional elastic–plastic finite element calculation results, but the magnitude is too large. In addition, when considering the rheological characteristics of the structural plane, the increase in valley shrinkage deformation value further increases the stress and deformation of the high arch dam, which can better reflect the dam's working behavior and ensure the dam's safe operation.

Effects of slope vegetation patterns on erosion sediment yield and hydraulic parameters in slope-gully system

Slope-gully system is an important watershed component of the Loess Plateau and the main source of erosion and sediment yield in small watersheds. Its forest and grass measures are of great significance to vegetation restoration and reconstruction and water and soil conservation. In the experiment, the effects of different slope vegetation patterns (upper slope, middle slope, lower slope, bare slope) on hydrodynamic characteristics and sediment yield of slope-gully system were studied by field flushing test under the condition of 75 % vegetation coverage and 12 L/min discharge. The results showed that: (1) Vegetation distribution in the lower part of the slope had the most obvious effect on reducing runoff shear force while vegetation distribution in the middle of the slope had the most obvious effect on reducing runoff power of the slope-gully system. (2) The water storage benefits of vegetation distributed on upper slope, middle slope, lower slope was 88 %, 87 %, and 81 %, and the benefits of sediment reduction was 96 %, 98 %, and 97 % (compared with bare slope). (3) The sediment reduction effect of the slope-gully system under different slope vegetation patterns is better than the water storage effect. On the whole, the effect of soil and water conservation was best when the vegetation was placed in the middle and lower of the slope. The results of this study provide a scientific basis for optimizing vegetation allocation in the Loess Plateau and promote the effective development of soil and water conservation.

Effects of shell sand content on soil physical properties and salt ions under simulated rainfall leaching

To reveal the influence of shell sand content on soil physical properties and salt ion changes under simulated rainfall leaching conditions, various ratios of shell sand to fluvo-aquic soil were simulated to change the particle composition of shell sand. Basic physical and chemical properties, such as soil particle-size composition, soil bulk density, soil porosity, soil pH, soil electrical conductivity, and soil salt ions were determined and analyzed. Fuzzy mathematics was used to evaluate the potential for soil water storage and salt suppression by altering the shell sand-to-fluvo-aquic soil ratio. The results showed that with decreasing shell sand content, the soil particle composition with different ratios of shell sand to fluvo-aquic soil changed significantly. With decreasing shell sand content, bulk density and capillary porosity of the soils with different ratios increased, and the total porosity and noncapillary porosity decreased. The soil pH first decreased and then increased, following the order 0:1 > 1:0 > 1:1 > 1:2, while the electrical conductivity increased. Cl−, NO3−, Na+, Ca2+, and Mg2+ showed a trend of first decreasing and then increasing with decreasing shell sand content, following the order 0:1 > 1:0 > 1:2 > 1:1. The mixed soil with a 1:1 ratio of shell sand and fluvo-aquic soil has the largest leaching loss of salt segregants. A comprehensive evaluation of the soil improvement performance with respect to the ratio of shell sand to fluvo-aquic soil revealed a trend of 1:1 > 1:0 > 0:1 > 1:2, and the mixed soil with a 1:1 ratio of shell sand to fluvo-aquic soil showed the greatest improvement. The shell sand content can significantly affect soil water and salt transport, and a suitable shell sand content can effectively improve soil water storage and salt inhibition effects.

Spatially-Resolved Integrated Precipitation-Surface-Groundwater Water Isotope Mapping From Crowd Sourcing: Toward Understanding Water Cycling Across a Post-glacial Landscape

Isotopic analyses of δ18O and δ2H of water in the context of the hydrologic cycle have allowed hydrologists to better understand the portioning of water between the different water domains. Isoscapes on a large spatial scale have been created to show isotopic variation in waters as a function of elevation, temperature, distance to coast, and water vapor source. We present the spatial and temporal isotopic results of precipitation, surface water, and groundwater of an ongoing study across Massachusetts, USA in order to establish an isotopic baseline for the region. This represents one of the most comprehensive and detailed isotopic studies of water across a 10,000 sq mi area that has exhaustively sampled important components of the terrestrial hydrologic cycle (precipitation, groundwater, and surface waters). We leverage the support of volunteers and citizen scientists to crowd source samples for isotopic analysis. The database consists of water samples from 14 precipitation sites, 409 ground water sites and 516 surface water sites across the state of Massachusetts, USA. The results indicate that groundwater isotopic composition ranges from δ18O −11 to −4‰ surface water ranges from δ18O −13 to −3.84‰ and precipitation ranges from δ18O −17.88 to −2.89‰. On a first order, the small bias of mean groundwater (−8.7‰) and surface water (−8.0‰) isotopes compared to precipitation δ18O (−7.6‰) supports that groundwater recharge and surface water storage effects through the hydrologic year impact the isotopic composition of surface and groundwater. While differences are distinct, they are larger than previously reported values, but still suggest more importance of summer precipitation than previously acknowledged. On average seasonal amplitudes of precipitation (2.7‰), surface water (1.13‰), and groundwater (~0‰) of the region demonstrate young water fractions of surface water to be 40% with groundwater ~0%. Results demonstrate that mean δ18O in precipitation, surface water and groundwaters are more enriched in heavy isotopes in areas near the coast, than the interior and western portion of Massachusetts. The hope is for this dataset to become an important tool for water management and water resource assessment across the region.

Mulching Measures Improve Soil Moisture in Rain-Fed Jujube (Ziziphus jujuba Mill.) Orchards in the Loess Hilly Region of China

Water shortage is the main bottleneck restricting the sustainable development of rain-fed jujube (Ziziphus jujuba Mill.) orchards in the loess hilly region of China. Given the effect of mulching on soil moisture conservation, straw mulching (SM) and jujube branch mulching (BM) were applied to a rain-fed jujube orchard in this study. Soil moisture dynamics, soil water storage, water consumption, and soil moisture attenuation after typical rainfall under SM, BM, and clean tillage (CT) were studied. The results showed the following: (1) The 0–60 cm soil layer was the seasonal fluctuation layer of soil moisture under SM, BM, and CT in both the normal precipitation year and the dry year studied. The moisture contents of the 0–60, 60–160, and 160–280 cm soil layers under SM and BM were higher than that under CT in the three experimental years studied, and SM showed the most obvious effect of increasing soil moisture. (2) SM and BM showed a significant soil water storage effect in all of the jujube growth stages, and SM had a better water storage effect than BM. (3) SM reduced the amount of water consumption by 94.3, 60.8, and 121.3 mm compared to CT in the whole jujube growth period in 2014, 2015, and 2016, respectively. The amount of water consumption of BM decreased by 34.8 and 31.0 mm compared to that of CT in the whole growth period in 2014 and 2015, respectively. (4) CT had the maximum soil moisture loss rate under continuous drought after rainfall. The soil moisture loss rate of CT was above 37.3% on the eleventh day after typical rainfall in 2014, 2015, and 2016. With the extension of drought, the soil moisture loss rate under SM increased slowly. This study suggests that SM is the best mulching measure for rain-fed jujube orchards, and pruned jujube branches can also be used for in situ mulching to obtain a certain moisture conservation effect.

A Unified Multiple Transport Mechanism Model for Gas through Shale Pores

Predicting apparent gas permeability (AGP) in nanopores is a major challenge for shale gas development. Considering the differences in the gas molecule-pore wall interactions in inorganic and organic nanopores, the gas transport mechanisms in shale remain unclear. In this paper, gas flow channels in shale, which are separated into inorganic pores and organic pores, are treated as nanotubes. Inorganic pores are assumed to be hydrophilic, and organic pores are assumed to be hydrophobic. In organic pores, multiple bulk free gas and surface adsorbed gas transport mechanisms are incorporated, while the bulk gas and water film are considered within inorganic pores. This paper presents a unified multiple transport mechanism model for both organic nanopores and inorganic nanopores. Unlike the earlier models, the presented models consider the absorption, stress dependence, real gas, and water storage effects on gas transport comprehensively for the entire flow regime. The results are validated with published data which is more in line with the real situation. The results show that (1) the AGP decreases gradually as the pore pressure decreases but that the decrease is sharp in small pores, (2) the AGP decreases dramatically when considering the real gas effect at 50 MPa in a 2 nm pore size, and (3) for a small pore size at the critical high-water saturation, AGP might increase suddenly as the flow regime changes from continuum flow to slip flow. The findings of this study can help for better understanding of the gas transport mechanisms for the entire flow regime in shale.

Effects of Conservation Tillage on Soil Physicochemical Properties and Crop Yield in an Arid Loess Plateau, China

Conservation tillage can improve soil physical structure and water storage, protect moisture, and increase crop yield. However, the long-term adoption of a single tillage method may have some adverse effects on soil and ecological environment, although crop yields have increased. Through informed allocation of soil tillage techniques, the combination and configuration of soil tillage measures, such as rotary tillage, subsoiling, and no tillage may reduce the shortcomings of traditional long-term farming. To explore the long-term production mode suitable for production of maize in the loess dryland area, a long-term experiment was conducted in Fuping County, Shaanxi Province, from 2013 to 2018. Six farming modes were used in the experiment: no tillage/subsoiling (N ↔ S), subsoiling/rotary tillage (S ↔ R), rotary tillage/no tillage (R ↔ N), continuous no tillage (N ↔ N), continuous subsoiling (S ↔ S), and continuous rotary tillage (R ↔ R). The changes in soil physical and chemical properties, soil water use patterns, soil water storage, conservation effects during the fallow and growth period, and the effects on farmland yield increase were analyzed. The results showed that rotary tillage can effectively improved soil structure and reduced soil bulk density, where N ↔ S treatment soil bulk density is low and in 0–60 cm soil layer averaged 1.31 g/cm3. Different tillage treatments could be used during the fallow period to store additional soil moisture: the N ↔ S treatment showed good water storage effect. Compared to traditional tillage, different tillage methods provided better soil moisture conditions for crops during the growth period, where N ↔ S treatment showed good soil moisture status during the growth period of spring maize. Among all the treatments, N ↔ S treatment effectively increased the organic carbon storage in the 0–60 cm soil layer, which was 54.3 t/hm2. Compared with traditional tillage, different tillage treatments effectively increased plant height and dry matter accumulation of spring maize, where N ↔ S treatment was found to be the best. Compared with the traditional rotary tillage model, the N ↔ S treatment significantly increased crop yield and water use efficiency (WUE) in continuous cropping fields of corn, the average yield of spring corn was 9340.2 kg/hm2, and the average WUE was 22.9 kg/(hm2·mm). In summary, for long-term sustainable development, the N ↔ S model is the best rotational tillage mode for continuous maize cropping in loess soil.

Seasonal persistence of soil moisture anomalies related to freeze\u2013thaw over the Tibetan Plateau and prediction signal of summer precipitation in eastern China

Soil moisture can be an effective climate prediction signal due to its long memory. This study investigated seasonal persistence of soil moisture anomalies from the preceding autumn to spring dominated by the soil freeze–thaw (FT) process over the Tibetan Plateau (TP), and their relationship with summer precipitation in eastern China. Results demonstrated that soil moisture anomalies from the preceding autumn can persist until spring by water storage effect of the soil FT process. Soil moisture in the TP during the preceding autumn and winter had similar climatic effects as spring soil moisture. Positive soil moisture anomalies in the eastern TP during the spring led to less summer precipitation in south China and the Yellow River basin, and more summer precipitation in the Yangtze River basin and northeast China. A possible mechanism for this was that wetter soil moisture anomalies from the preceding autumn were stored in the soil by soil freezing, and were released with soil thawing in the spring, inducing surface diabatic heating anomalies over the TP. These anomalies then persisted into summer and enhanced the TP’s thermal forcing to the subtropical westerlies and affected stationary Rossby wave train propagation in middle latitudes, particularly on the northwest and northeast sides of the TP. This study suggests that most of spring soil moisture anomalies signal contains the preceding two seasons’ soil moisture anomalies information; therefore, summer precipitation predicting signals can be obtained from soil moisture anomalies from the preceding autumn, which could lengthen the seasonal climate prediction period.

Water storage effect of soil freeze-thaw process and its impacts on soil hydro-thermal regime variations

In the soil freeze/thaw phenomenon, the soil water phase and energy budget change, which can affect the soil-vegetation-atmosphere system. Herein, the basic role of freeze–thaw–process (FTP) in soil water and heat transport and its impact on soil moisture and temperature variation were investigated using the observations and numerical experiments with and without FTP in Community Land Model version 4.5 (CLM4.5) on the Tibetan Plateau (TP). The results averaged over the whole TP revealed that no soil FTP (i.e., no water phase change occurred) resulted in lower surface soil temperature by about -1.02 ℃ in freeze-thaw (FT) period, while surface soil temperature is higher by about 0.91 ℃ and surface soil moisture is drier by about -0.02 mm3/mm3 in after-thaw (AT) period. Soil FTP has a water storage effect, the storage index (SI) can reach 0.95 at surface layer. Without soil FTP, the surface soil water content at the AT period can be reduced by ∼10% (SI is decreased by about -0.05) as a result of enhanced evaporation; the soil moisture memory was shortened by about -20 days in March. Accordingly, surface latent heat decreased by -1.07 W/m2, while the surface sensible heat increased by 4.72 W/m2. The effects of FTP on soil water and heat transport at deep layer are distinguished from that at the surface layer. These imply that the biases of soil temperature and moisture simulation in models during FT period could lead to large uncertainties in estimating climate effects of TP. Under climate warming background in recent decades, with the delaying of soil freeze-beginning date and advancing of soil thaw-end date, changes of soil FTP regime would lead to loss of spring soil moisture.

Regulatory effects of bundled straw covering on winter wheat yield and soil thermal-moisture utilization in dryland.

Bundled straw covering (BSC), using corn whole straw for partial coverage planting, is a novel dryland cultivation technique. To examine the effects of BSC on the thermal-moisture status and winter wheat yield under typical arid and semiarid conditions in the Loess Plateau of Northwest China, soil temperature, soil water content and consumption, grain yield and water-use efficiency were compared for four treatments, including no-tillage with straw mulch (NTS), whole field plastic mulching with soil covering on the top of the plastic mulch and bunch-seeding (PFM), open field cultivation (CK) and BSC during three growing seasons from 2013 to 2016. The results showed that PFM significantly increased soil temperature of 5-20 cm depth before jointing stage, while the warming effect of BSC and NTS was mainly in the wintering period. The three kinds of coverage methods after jointing stage had significant cooling effects. Both BSC and PFM significantly improved soil water storage effect during the fallow period. BSC significantly elevated soil moisture in the depth of 0 to 200 cm in the whole growing season. The improvement of soil moisture by PFM and NTS mainly occurred before the heading stage, and soil moisture in PFM treatment gradually decreased after heading stage. BSC and PFM significantly increased water consumption in the whole growth period and increased that during the jointing stage to the flowering stage, and promoted the utilization of soil moisture below 120 cm. Compared with CK, BSC, NTS and PFM significantly increased the number of panicles per unit area and biomass at maturity. In those three treatments, grain yield was increased by 19%-52%, 14%-30% and 15%-60%, respectively, and the annual water use efficiency was increased by 19%-61%, 14%-31% and 15%-58%, respectively. BSC had the same potential for increasing yield and water use efficiency as PFM. Based on factors such as winter wheat yield, soil thermal-moisture utilization and annual water consumption, BSC is a high-yield and efficient cultivation method that is conducive to the sustainable development of dryland agriculture in Northwest China.

Experimental study on destruction of thermal stratification tank in solar collector performance

Destructing thermal stratification of water storage tank and effect on solar collector performance was investigated experimentally. First experiment was performed using conventional thermosyphon flow of water. In the second experiment, without discharging the hot water storage tank of the previous day, the experiment was continued. Third and fourth experiments were started with similar condition to the first case. However, in the third case during the experiment, the tank’s water mixed using a circulating pump and in the fourth case, fresh water was replaced at three different times with the same amount from tank’s water. Results indicated lowering the temperature of the lower layers in the tank would enhance the solar collector performance. Collector performed accordingly from best to worst; the three times tank discharge, conventional, water flow circulation, and initially charged tank recharge. For example, at 16:00, the collector’s efficiencies for three-time tank discharge, normal, and destruction of thermal stratification experiments were 52.9%, 38.3%, and 32%, respectively. Further, at 17:00, the collector’s efficiency for three-time discharge indicated 36% while nearly zero for other experiments was obtained. In addition, for heat absorption and collector’s efficiency study, the theoretical results compared with the experimental results.

A Simple Representation of Plant Water Storage Effects in Coupled Soil Water Flow and Transpiration Stream Modeling

Core Ideas A previous soil water flow model was extended to allow simulation of transient plant water storage. Comparison with measured Norway spruce sap flow data indicates improved model performance. The proposed algorithm can be easily incorporated into existing soil water flow models. When describing the movement of water in a variably saturated plant root zone, most existing hydrological models use the assumption of quasi‐steady‐state flow to relate root water uptake to canopy transpiration, thereby neglecting the effect of changing plant water storage. This approach is known to be problematic, especially when considering relatively large volumes of water stored in the tissues of tall trees. We propose a simple algorithm, based on the concept of whole‐plant hydraulic capacitance, to deal with the problem. The algorithm is implemented in a one‐dimensional soil water flow model involving vertically distributed macroscopic root water uptake. In this study, the proposed transient storage approach was compared with the quasi‐steady‐state approach. Both approaches were used to simulate soil water flow and diurnal variations of transpiration at a forest site covered with Norway spruce [Picea abies (L.) H. Karst.]. The key parameter of the transient storage approach, the plant hydraulic capacitance, is estimated by comparing the variations in the potential transpiration rate, derived from micrometeorological measurements, with observed sap flow intensities. The application of the proposed algorithm leads to more realistic predictions of root water uptake rates at the site of interest. The inclusion of the plant water storage effects improved the ability of the model to capture the anticipated diurnal variations in actual transpiration rates. The algorithm can be easily implemented into existing soil water flow models and used to simulate transpiration stream responses to varying atmospheric and soil moisture conditions including isohydric and partly also anisohydric plant responses to drought stress.

Modelling of global mass effects in hydrology, atmosphere and oceans on surface gravity

We present a MatlabTM/Octave-based software tool mGlobe to compute the effect of atmospheric, continental water storage, and non-tidal ocean mass variations on surface gravity. These effects must be considered or reduced prior to any analysis of geophysical phenomena using observations of superconducting gravimeters. Contrary to the alternative providers, mGlobe allows the computation for an arbitrary location worldwide, supports a larger number of input models and offers more flexibility in terms of computation settings. The high number of supported models is important for assessment of model uncertainties. Discrepancies exceeding 75% were found. The continental water storage effect showed low sensitivity to spatial and temporal resolution. The deficient temporal resolution affects the non-tidal loading and atmospheric effects significantly. The same holds true for the influence of the spatial resolution on atmospheric effects. To compensate this effect, we introduce a site-specific correction factor based on differences between the real topography and model's orography.

Biological and physicochemical properties of carbon-graphite fibre-reinforced polymers intended for implant suprastructures

The aim of this study was to determine water sorption, water solubility, dimensional change caused by water storage, residual monomers, and possible cytotoxic effects of heat-polymerized carbon-graphite fibre-reinforced composites with different fibre loadings based on methyl methacrylate/poly(methyl methacrylate) (MMA/PMMA) and the copolymer poly (vinyl chloride-co-vinyl acetate). Two different resin systems were used. Resin A contained ethylene glycol dimethacrylate (EGDMA) and 1,4-butanediol dimethacrylate (1,4-BDMA); the cross-linker in Resin B was diethylene glycol dimethacrylate (DEGDMA). The resin mixtures were reinforced with 24, 36 and 47 wt% surface-treated carbon-graphite fibres. In addition, polymer B was reinforced with 58 wt% fibres. Water sorption was equal to or below 3.34±1.18 wt%, except for the 58 wt% fibre loading of polymer B (5.27±1.22 wt%). Water solubility was below 0.36±0.015 wt%, except for polymer B with 47 and 58 wt% fibres. For all composites, the volumetric increase was below 0.01±0.005 vol%. Residual MMA monomer was equal to or below 0.68±0.05 wt% for the fibre composites. The filter diffusion test and the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay demonstrated no cytotoxicity for the carbon-graphite fibre-reinforced composites, and residual cross-linking agents and vinyl chloride were not detectable by high-performance liquid chromatography (HPLC) analysis.

Improvement of Volume Stability in Core Concrete of Concrete-Filled Steel Tube

Due to the concrete self-shrinkage, frequent load application and temperature fluctuation, and so on，the gap formed between the inner tube wall and the core concrete surfaces would decrease the performance of concrete-filled steel tube (CFST). To prevent this cavity problem, various types of expansive agents and aggregates were used in this study to improve the volume stability of core concrete. Comparative experiments with mortars and concrete were carried out respectively under standard curing condition and under enclosed curing condition which simulated the environment in steel tube. The results could be summarized as follows: ● Two types of expansive agents, ZY type expansive agent mainly containing sulfates and aluminates and M type expansive agent mainly containing magnesium oxide, presented different expansive behaviors with curing ages in mortar and concrete. Two types of expansive agents combined with each other could produce complementary and superimposition effects to improve continuously the volume stability of mortar and concrete. ● Sufficient water supply is the key factor for the formation and maintenance of expansion. The volume change caused by the self-shrinkage effect of core concrete could not be effectively off-set with whether two types expansive agents or their compounds under enclosed environment in which water was scarce and could not be supplied from outside. ● When some water-saturated ceramsite were used to partially replace aggregates in core concrete,the volume expansion performance of core concrete improved dramatically with the water storage and supply effects of water-saturated ceramsite.

Terrestrial waters and sea level variations on interannual time scale

On decadal to multidecadal time scales, thermal expansion of sea waters and land ice loss are the main contributors to sea level variations. However, modification of the terrestrial water cycle due to climate variability and direct anthropogenic forcing may also affect sea level. For the past decades, variations in land water storage and corresponding effects on sea level cannot be directly estimated from observations because these are almost unexistent at global continental scale. However, global hydrological models developed for atmospheric and climatic studies can be used for estimating total water storage. For the recent years (since mid-2002), terrestrial water storage change can be directly estimated from observations of the GRACE space gravimetry mission. In this study, we analyse the interannual variability of total land water storage, and investigate its contribution to mean sea level variability at interannual time scale. We consider three different periods that, each, depend on data availability: (1) GRACE era (2003–2009), (2) 1993–2003 and (3) 1955–1995. For the GRACE era (period 1), change in land water storage is estimated using different GRACE products over the 33 largest river basins worldwide. For periods 2 and 3, we use outputs from the ISBA-TRIP (Interactions between Soil, Biosphere, and Atmosphere—Total Runoff Integrating Pathways) global hydrological model. For each time span, we compare change in land water storage (expressed in sea level equivalent) to observed mean sea level, either from satellite altimetry (periods 1 and 2) or tide gauge records (period 3). For each data set and each time span, a trend has been removed as we focus on the interannual variability. We show that whatever the period considered, interannual variability of the mean sea level is essentially explained by interannual fluctuations in land water storage, with the largest contributions arising from tropical river basins.

Terraced paddy field rainfall-runoff mechanism and simulation using a revised tank model

Terraced paddy fields play important roles in water and soil conservation because their water storage effect reduces and delays flood peaks. This study applies the terraced paddy field rainfall-runoff mechanism to the tank model. Though the traditional four-section tank model can easily simulate rainfall-runoff in a terraced paddy field, it has many parameters that are difficult to calibrate. To address the shortcomings of the traditional four-section tank model, this study develops a revised tank model to simulate rainfall-runoff. This study selects a terraced paddy field located in Hsuing-Pu village in Hsiuing-Chu County as the experimental field. The field under investigation was equipped with automatic monitoring stations, water-stage, and rain gauges. These stations collected data on rainfall and water flow to simulate the rainfall-runoff model in that region. To simulate the runoff behavior of the experimental terraced paddy field, two rainfall events were selected from the gathered data and five normal evaluation indexes based on static and hydrological theory were applied to calculate the results of simulation simultaneously. The revised tank model performed better than expected, and precisely predicted the variations and trends in flow charge. Comparison with representation indexes proved that the revised tank model is an appropriate and valuable tool for rainfall-runoff simulation.

Simulated soil water storage effects on streamflow generation in a mountainous snowmelt environment, Idaho, USA

AbstractAlthough soil processes affect the timing and amount of streamflow generated from snowmelt, they are often overlooked in estimations of snowmelt‐generated streamflow in the western USA. The use of a soil water balance modelling approach to incorporate the effects of soil processes, in particular soil water storage, on the timing and amount of snowmelt generated streamflow, was investigated. The study was conducted in the Reynolds Mountain East (RME) watershed, a 38 ha, snowmelt‐dominated watershed in southwest Idaho. Snowmelt or rainfall inputs to the soil were determined using a well established snow accumulation and melt model (Isnobal). The soil water balance model was first evaluated at a point scale, using periodic soil water content measurements made over two years at 14 sites. In general, the simulated soil water profiles were in agreement with measurements (P < 0·05) as further indicated by high R2 values (mostly > 0·85), y‐intercept values near 0, slopes near 1 and low average differences between measured and modelled values. In addition, observed soil water dynamics were generally consistent with critical model assumptions. Spatially distributed simulations over the watershed for the same two years indicate that streamflow initiation and cessation are closely linked to the overall watershed soil water storage capacity, which acts as a threshold. When soil water storage was below the threshold, streamflow was insensitive to snowmelt inputs, but once the threshold was crossed, the streamflow response was very rapid. At these times there was a relatively high degree of spatial continuity of satiated soils within the watershed. Incorporation of soil water storage effects may improve estimation of the timing and amount of streamflow generated from mountainous watersheds dominated by snowmelt. Copyright © 2008 John Wiley & Sons, Ltd.

Water storage effect on marginal adaptation

Water storage effect on marginal adaptation

Impact of hillslope vegetation restoration on gully erosion induced sediment yield

Facing the eco-environmental construction on the Loess Plateau, especially the vegetation restoration in the semiarid areas, as well as the dam system engineering construction that is about to start, how can the vegetation restoration gain the optimum ecological benefits following the improvement of the preservation rates of trees and grass on the basis of guaranteeing water storage and silt trapping effects? What techniques should be taken to restore vegetation? These questions critical to environmental management on the Loess Plateau have to be settled urgently. According to the different macroscopic spatial distribution patterns of forest and grass on the Loess Plateau, this paper analyzes the macroscopic hillslope and gully management relationship in the middle Yellow River and weight of natural and human factors in erosion-induced sediment yield in the context of environmental background of the major silt producing areas. In light of the current status of the integrated management of small watersheds and soil and water conservation measure arrangement schemes of hillslopes and gullies on the Loess Plateau, this paper discusses the impact of vegetation restoration on gully erosion induced sediment yield and the effect of vegetation caused sediment reduction. Studies indicate that there exists an erosional environmental background related to the natural and human activities in the sediment yield peak values of the sandy and coarse sandy areas in the middle Yellow River, sediment yield modulus is closely related to the synthetic effect of environmental elements, and the rainstorms, reclamation rate and forest coverage are the main factors affecting sediment yield modulus in the sandy and coarse sandy areas. The key to control soil erosion in the sandy and coarse sandy areas is the conversion of farmland into forestland and grassland, the reduction of reclamation rate and the increase of tree and grass vegetation. Small catchment management should adhere to the principle of simultaneous control of hillslope and gully erosion and combination of biological measures with engineering measures. Engineering measures play an important role in the hillslope vegetation restoration in the initial period. Vegetation restoration can result in a reduction of erosion induced sediment yield in gullies of Yangjiagou by over 75%.