Water Loss Process Research Articles

Stable Isotopes Constrain Water Seepage From Gnammas Into Bare Granitic Bedrock

AbstractSubtle bedrock depressions called gnammas allow the water in ephemeral pools to maintain contact with bare rock, thus serving as natural rock‐weathering experiments. Following filling by precipitation, evaporation is often assumed to be the sole process of water loss from gnammas. We evaluated this assumption by monitoring evolving stable isotope compositions of gnamma waters hosted in granite of Colorado's Front Range. Surprisingly, we found that a significant fraction of the water was lost by seepage through the underlying bedrock. Seepage dominated, with only 10%–20% loss by evaporation. We propose a conceptual model of gnamma formation in which enhanced weathering of the bedrock beneath the gnamma increases the water holding capacity and permeability of the underlying rock that in turn promotes efficient water loss through seepage and further weathering of the surrounding rock. This model has implications for bare‐rock weathering and hence the evolution of landscapes over geologic timescales.

Effects of rainfall, sediment source–sink landscape, and hydrological connectivity on runoff more than sediment in a karst basin

AbstractUnderstanding the mechanisms underlying soil and water loss in karst basins is beneficial for water resources management and soil and water loss conservation. However, the effects of rainfall, sediment source–sink landscape, and hydrological connectivity on runoff sediment characteristics in karst basins are unclear. This study used sediment source–sink landscape and hydrological connectivity theories and a generalized additive model to analyze the changes and combined effects of sediment source–sink landscape patterns, hydrological connectivity, and rainfall on runoff sediment from 2000 to 2020 in the Yeji River basin in the karst region of southwest China. The results indicated that the average sediment transport modulus and runoff modulus in the Yeji River basin during 2000–2020 were 144 t·km−2·a−1 and 15 L·s−1·km−2, respectively. The karst surface and subsurface double‐layer hydrological structure resulted in a lower sediment transport modulus than in non‐karst areas. The sediment‐source landscape area decreased, sediment‐sink landscape area increased, and sediment source–sink landscape load ratio index slightly increased. Hydrological connectivity exhibited a decreasing trend over time, but the overall change was small. Changes in source–sink landscape patterns significantly affected hydrological connectivity. As the main affecting factor, rainfall and its combined effects with sediment source–sink landscape patterns and hydrological connectivity explained 85% and 95% of the variances in runoff, and 40% and 63% of the variances in sediment, respectively. These results suggest that a rational layout of the sediment source–sink landscape can effectively improve hydrological connectivity and regulate the soil and water loss process. Our findings have important implications for karst basin ecological restoration and protection.

Water balance analysis in a novel pilot-scale of the Worm-sludge treatment reed bed (W-STRB) planted with Arundo donax

A one-year study of sludge treatment reed bed assisted with earthworms (W-STRB) was conducted in a temperate climate. The effects of using Eisenia fetid and Arundo donax on W-STRB water balance (WB) and dewatering efficiency (DE) were investigated. Four different bed configurations were tested: worm-planted (WP), planted (P), worm-control (W), and control (C), duplicated resulting in a total of eight units. The beds received a total of 24 cycles of mixed sewage sludge twice per month (average loading rate: 43.59 kg.DS. m−2.year−1). It was found seasonal variation played a significant role in WB and DE. During the dry season, the thickness of the residual sludge (RS) layer was less than 1 cm, with a dry solid (DS) content of over 80%, in contrast, the wet season indicated an increase in RS thickness to nearly 30 cm (DS < 15 % for all units). The WP unit exhibited the lowest RS accumulation, 22% less than the P, W, and C units. The subsurface layer had a 5% lower volatile solids (VS) content compared to the surface layers. After 132 days of a final resting, WP unit had the highest RS volume reduction of 65 % (DS = 71 % and VS = 53 %) and a RS thickness of 6 cm indicating a 10 % higher stabilization compared to P unit. The population of earthworms was 30% higher in the WP unit compared to the W unit. As the subsurface DS exceeded 20 % during the dry season, the population increased. The WP unit showed a 43% higher above-ground plant biomass compared to the P unit. In WB analysis, evapotranspiration (ET) was 46% higher in the WP unit (average daily ET = 5.44 mm in the dry season). The main process of water loss was through drainage and Awhile water content in RS layer was 57 % during feeding period. The water percolation rate of all units decreased by 99%, particularly during the wet season, reaching less than 0.1 m.day−1.

Numerical Simulation of Ground Subsidence Factors Resulting from Unpressurized Pipeline Rupture Below the Water Table

The rupture of an unpressurized pipeline below the water table can lead to the leakage of groundwater along with soil particles into the pipeline. This not only causes blockages in the pipeline but, more critically, can result in ground subsidence. Understanding the factors influencing this phenomenon is a subject of great interest. To delve into this matter, this study employs the DEM-CFD methodology to synergistically encompass particle dynamics and interactions within the flow domain. It introduces an innovative framework for simulating water and soil erosion subsequent to the rupture of subaqueous unpressurized pipelines. This pioneering approach introduces a novel modeling and simulation paradigm catering to the analysis of intricate phenomena of this nature. Upon validating the flow field, our investigation specifically focused on three key factors: particle friction coefficient, groundwater level, and particle size distribution. We conducted a thorough examination of the process and mechanism of water and soil loss at the pipeline leakage point and the subsequent development of stratum subsidence. Our results indicate that particles with a friction coefficient of 0.6 had a reduced maximum displacement by 8.9%, compared to particles with a friction coefficient of 0.3. Similarly, a groundwater depth of 2 m resulted in a 29.6% decrease in maximum displacement compared to a 4 m depth, with a corresponding 160.9% increase in maximum force chain strength. Discontinuous particle gradation, in contrast to continuous gradation, yielded a notable 40.3% reduction in maximum displacement and a substantial 495.1% increase in maximum force chain strength. This underscores the noteworthy influence of particle friction coefficient, groundwater table elevation, and soil particle diameter on the stability of the overlying soil strata in the vicinity of a compromised unpressurized conduit.

Effect of vibration and broken cold chain on the evolution of cell wall polysaccharides during fruit cucumber (Cucumis sativus L.) shriveling under simulated transportation

The fruits and vegetables often result in shriveling, which can significantly affect the quality in terms of texture, appearance, and saleable weight during transportation and storage. In this study, fruit cucumbers (Cucumis sativus L.) were subjected to vibration followed by storing them under isothermal and non-isothermal conditions (simulated broken cold chain) for 15 days. Water movement, cell wall polysaccharides and degrading enzymes, cell wall structure of cucumbers were determined. The findings revealed that water initially migrated from the inner pericarp of cucumber. Vibration and broken cold chain damaged the fruit cell wall and cell wall polysaccharides, and increased degrading enzymes, which promoted the water movement from the tissues to the exterior, causing severe shriveling of cucumber. Firmness loss accompanied with cucumber shrivel appeared by as early as 6 days of storage after vibration (5.5 Hz), with decrease of 19.88–29.93 %. However, this phenomenon was not observed in the control cucumber until 12 days after storage with firmness of 8.22 N. Therefore, this study shows that simulated transport vibration and broken cold chain could cause intracellular damage in cucumber tissues, which expedites the process of water loss, degradation of cell wall polysaccharides and shriveling process. The study also reveals that precise temperature control and avoiding vibration of transportation in cold chain logistics of cucumbers are important in maintaining the product quality during storage and transport.

Indoor Experiments on the Moisture Dynamic Response to Wind Velocity for Fuelbeds with Different Degrees of Compactness

The semiphysical method is presently the most widely used for predicting litter moisture content, but it produces some errors. These are mainly due to the simplification of the water loss process and not accounting for the fuelbed structure, which can have a serious impact on the accuracy of litter moisture content predictions and, consequently, on forest fire management. As such, in this study, we constructed fuelbeds with different degrees of compactness, and the moisture content is saturated at this time. The drying process is recorded every 10 min under different wind velocity, and the experiment is stopped when the moisture content is not changing. Taking the saturated fibers’ moisture content (30%) as the threshold value, the drying process was artificially divided into two stages (from the initial moisture content to 30%, it is a process of free water drying, and from 30% to the equilibrium moisture content, this is the process of drying of bound water), which is called the distinguishing drying process. The whole drying process (from the initial to the equilibrium moisture content) is called the undistinguishing drying process. Drying coefficient and effect factors were calculated by distinguishing and not distinguishing the drying process, respectively. This established a prediction model based on compactness and wind velocity. The results show that the drying coefficients, k2 and k, of the two litter types were significantly different: the k2 of the white oak fuelbed was significantly lower than its k, with a maximum variation difference of 57.10%. The k2 in the Masson pine fuelbed was significantly higher than its k, with a maximum variation difference of 72.76%. Wind velocity and compactness had significant effects on all the drying coefficients of the two litter types, but with changes in the effect factors. The changes in k2 were weaker than those of the other drying coefficients. Compared with the model that did not distinguish the drying process, the MRE of the prediction models for white oak and Masson pine decreased by 27.39% and 2.35%, respectively. The prediction accuracy of the model of the drying coefficient obtained by distinguishing the drying loss process was higher than that of the model that did not distinguish the drying process. This study was an indoor simulation experiment that elucidated the drying mechanism of litter and established a prediction model for the drying coefficient based on effect factors. It is of great significance for further field verification and for improving the accuracy of moisture content predictions based on the semiphysical method and will significantly improve the accuracy of fire risk and fire behavior prediction.

DeepEvap: Deep reinforcement learning based ensemble approach for estimating reference evapotranspiration

Precision agriculture aims to increase crop yield by employing an efficient resource management scheme, such as estimating irrigation requirements. Reference evapotranspiration (ET0), defined as the process of water loss from the soil and reference plant, is one of the indispensable components on which crop irrigation requirement depends. It is mainly calculated by using empirical models. However, these models require a large climate dataset that is sometimes unavailable in data-scarce regions. The present study focuses on the estimation of ET0 values by using three climate parameters as input variables i.e., minimum temperature (Tmin), maximum temperature (Tmax), and solar radiation (Rs). Moreover, to consider the effect of time-varying characteristics of the ET0 process, deep reinforcement learning (DRL) based ensemble approach, DeepEvap, is introduced to estimate ET0 values. The whole modeling procedure of the proposed ensemble model incorporates three phases. In phase I, the data preprocessing technique is performed on the meteorological data to clean the existing impurities as it affects the performance of any machine learning (ML) based approach. In phase II, four different deep neural network-based models are used to build the estimation model of ET0 and calculate the prediction results. In phase III, the DRL approach is used to ensemble the prediction results of these four models. The meteorological dataset of two stations of India: Ludhiana and Patiala, is selected to validate the proposed approach. The results of the conducted study depict that: (a) The proposed DeepEvap approach is competitive for ET0 prediction by achieving a coefficient of determination (R2) = 0.96. It significantly outperforms four baseline models; (b) The proposed technique also integrates four deep neural network models and works better than existing ensemble approaches.

RWLMod-Potential Model to Study Plant Tolerance in Drought Stress Conditions.

Rationale: Water loss by evaporation is a normal physiological process, in order to regulate plant temperature. Under conditions of thermal and water stress, water loss is accelerated compared to normal conditions, and the response of plants is variable. In extreme cases, it can lead to wilting and death of plants. It was found that the phenomenon of water loss behaved as a pattern in different plant species, given by two functions, logistics (first part of water loss) and hyperbola (second part of water loss) in relation to a moment m, at which the rate of water loss (RWL) has reached its maximum value. Method: We studied the water loss process for a series of plant samples on different plant species (Picea abies L., H. Karst; Juniperus communis L.; Pinus silvestris L.; Thuja occidentalis L.; Lamium purpureum L.; Veronica hederifolia L.), measuring the rate of weight loss (RWL) in controlled conditions. The drying of the samples was done in identical conditions (thermo-balance, 100 °C, standard temperature for drying the plant samples) with the real-time recording of the drying time simultaneously with the water loss rate (RWL) from the plant samples. The exposure time varied, depending on each species sample, and was approximately 1000 s. Results: The experimental data was recorded at intervals of every 10 s, during the entire drying period. RWL values varied from 0.024 to 0.054 g/min at the beginning of the drying process and reached maximum values after 70–100 s, having values between 0.258 g/min and 0.498 g/min. During the drying period, this indicator presented different graphic evolutions, difficult to be described with a single function. The first segment was described by a logistic function, and the second was described by a hyperbola, resulting in a model (RWLMod) which described the real phenomenon. This model and theoretical calculation were used to quantify the water loss in a time interval and, compared with empirical dates, no significant differences were observed, which indicated an increased degree of accuracy regarding the use of this model. Recommendation and novelty of work: The novelty of the work is given by the obtained model (RWLMod), which makes possible the description of RWL over the entire time interval, and ensures a good fit with the real data. It recommends the method and model in studies of plant behaviour under stress in relation to different influencing factors.

THE APPLICATION OF DRY RUBBER LATEX AND VERMICOMPOST TO PLANT WATER CONSUMPTION AND THE GROWTH OF PADDY ON SWAMPY LAND

Swampy land is an alternative for rice plant cultivation where the amount of rainfall has an impact on the amount of inundation. In order to provide appropriate water for rice plants, especially during the dry season, an irrigation water system is required for its control.Alternative materials such as dry rubber latex and vermicom-post can be utilized to reduce water use and ensure that water is delivered as efficiently as possible. The goal of this study was to see how dried rubber latex on the soil surface and vermicompost in the soil affected rice plant water demand and growth. This research was conducted from November 2020 – February 2021. The study used a factorial randomized block design (RAKF) with 2 treatments, covered dry rubber latex variations (K), K0 (0%), K1 (25%), K2 (50%), K3 (75%), and vermicompos (V), V0(0 g), V1(58.82 g), V2(117.64 g), V3 (176.46 g)with 3 rep-licat. So that the total treatmentsare 48 treatments.The results showed that the application of dry rubber latex and vermicompost significantly affected the number of leaves and the number of tillers. The K3 treatment (75%) was the best because it had the smallest evapotranspiration rate with an average of 1.2 mm day-1. The K3 treatment (75%) had the smallest average water requirement of 1.6 mm day-1 with an average number of 37.07 leaves. The high yield of K3 treatment was due to the wider the area covered by 75% (K3), the higher the water content, nutrients, and the lower the soil temperature. Closure using dry rubber latex can reduce sunlight so that the process of water loss is lower, and the available nutrients are higher.

On the suitability of stacking-based ensembles in smart agriculture for evapotranspiration prediction

Smart agriculture aims at generating high harvest yields with an efficient resource management, such as the estimation of crop irrigation. One of the factors on which a productive crop irrigation depends on is evapotranspiration, defined as the water loss process from the soil. This is mainly measured by empirical equations, even though they are conditioned by the specific climatological variables they require. In recent years, data mining techniques are proposed as a powerful alternative to predict evapotranspiration. Among them, ensembles are notable in that they provide accurate estimators in different scenarios. Stacking is an ensemble-building technique aimed at strengthening the prediction capabilities of the system by the combined learning from the original features in the data and synthetic features created from the predictions of multiple models. This research proposes the usage of stacking for evapotranspiration prediction, which has been overlooked in the specialized literature, with the aim of a more sustainable management of water resources. The proposal is compared to other state-of-the-art empirical equations and data mining methods over several real-world climatological datasets of different agricultural areas in Spain. This comparison is performed considering separate datasets with features based on temperature, mass transfer, radiation and, finally, using the main meteorological variables together. The results obtained show that stacking is the best approach in all datasets and each group of features evaluated, running as good alternative to predict evapotranspiration when using data of a different nature and under different conditions.

Water loss and status in sponge cake: Impact of Eucheuma as a flour replacement.

The impact of Eucheuma on water loss and status in sponge cakes was measured and analyzed in this study. Eucheuma was used to replace 0%, 10%, and 20% of wheat flour to make sponge cakes, coded as the control, EP10, and EP20, respectively. The initial water content of batters showed no significant differences (around 57.0%, dry basis), whereas the final EP10 and EP20 products had higher water content. Three stages were found during baking in control sample and these three stages were fitted by linear, linear, and exponential models with root mean squared error (RMSE) of 0.016, 0.018, and 0.133, respectively. Eucheuma addition decreased the water loss rate and changed the water loss stages, which were fitted by linear, linear, and linear models in EP20 sample (RMSE = 0.027, 0.047, and 0.108, respectively). The crust formation and crumb structure analysis showed that the formation of cracks and the disappearance of pore structures hindered the water evaporation. The low-field proton nuclear magnetic resonance and magnetic resonance imaging results showed that the water status in the final EP20 products was not as tightly as that in the control samples. A proposed schematic diagram was developed based on the qualitative analysis of the transfer mechanisms to explain the total effect of Eucheuma on the water loss rate and status. These results aid our understanding of the water loss process of sponge cakes and promote the potential application of Eucheuma in bakery products. PRACTICAL APPLICATION: Eucheuma as a flour replacement can improve the contents of dietary fiber and minerals like potassium of sponge cake. The impact of Eucheuma on water loss and status in sponge cake was measured and analyzed in this study. The results can promote the potential application of Eucheuma in bakery products and predict the quality attributes of baking products.

An Instrument With Constant Volume Approach for In Situ Measurement of Surface Runoff and Suspended Sediment Concentration

AbstractThere is an increasing demand for reliable methods to measure soil loss in order to get a better understanding of sediment movement and to develop process‐based sediment transport models. This study described the design, calibration, and practical application of an instrumented technique that automatically characterized surface flow in situ fields. The instrument consisted of a sampling assembly, a measuring assembly, and a management platform. The special design combined with a volume‐mass conversion relationship was used to determine the exact volume and mass of the sediment‐laden water, thereby allowing the implementation of real‐time measurement and synchronous calculation of runoff rate and sediment concentration. Calibration results showed that normal distributions and an average error of −3.67% were obtained for the target sediment concentrations of 2–1,000 g/L. Compared with the gravimetric method, the average error of the new technique for sediment concentration was 4.82%, and the highest precision was 98.50%. The high repeatability and accuracy of the technique suggest that it can be used with confidence to give satisfactory results in fields. A field experiment under natural rainfall showed that a grass‐covered plot had 18.94% less runoff rate and 42.92% lower sediment concentration than a bare soil plot, illustrating the impact of vegetation cover on reducing soil loss. This uniquely designed instrument provides a new approach to real‐time sediment detection in surface flow. It will be beneficial for rigorously evaluating runoff and sedimentation and for in‐depth research regarding water and soil loss processes.

Effects of drying variables on the characteristic of the hot air drying for gastrodia elata: Experiments and multi-variable model

Energy saving and efficient drying model play important role in the extraction of high quality Chinese medicinal materials. In this work, the gastrodia elata was subjected to hot air drying of revealing the drying characteristics with the medicinal indicator of gastrodin ingredient. The multiple drying variables of drying temperature, air velocity, slice thickness and relative humidity were taken into account. Based on the experimental results, an optimized multi-variable model was established to predict the characteristics of drying the sliced gastrodia elata with hot air. The experimental results show that the optimal model of the Page model enables to predict the water loss process of the sliced gastrodia elata under multiple drying variables. The optimal drying variables were determined based on the maximum gastrodin content, of which the temperature was 60 °C, air velocity was 3.5 m/s, slice thickness was 0.4 cm and relative humidity was 25 %. Meanwhile, the drying quality was improved efficiently. The effective diffusion coefficient of gastrodia elata in the hot air drying ranged from 2.254 × 10−9 m2/s to 3.241 × 10−8 m2/s, and the dry activation energy was 34.16 kJ/mol.

Orthotropic Viscoelastic Properties of Chinese Fir Wood Saturated with Water in Frozen and Non-frozen States

Abstract In order to better understand the differences in orthotropic viscoelastic properties of Chinese fir (Cunninghamia lanceolata) in frozen and non-frozen states, the storage modulus (E′) and loss modulus (E″) of the longitudinal, radial, and tangential specimens were investigated under water-saturated conditions with temperatures ranging from −120°C (or 30°C) to 280°C. Results revealed that the order of magnitude in E′ for each orientation was consistent for temperatures below 0°C, while the anisotropy in E′ was reduced due to the enhancement effect of ice. Frequency-dependent γ-relaxation was observed at approximately −96°C for all orthotropic directions. A sharp discontinuity in E′ occurred at approximately 0°C for each specimen, together with the corresponding sharp peak in the E″ spectrum. Furthermore, the frozen free water had an effect on the orthotropic viscoelastic behavior in the water-saturated specimens within the range of −120°C to 280°C. Specimens with a frozen history leveled off at the initial temperature ramping phase for each orientation, while a frozen history reduced the decline in stiffness of the wood specimens. Similar to the variations in E′, the dramatic loss of water increased the complexity of the E″ values. The loss of free water also had a pronounced effect on the viscoelastic properties during the temperature ramping process. Thus, in the wood industry, it necessary to consider the variations in the orthotropic viscoelastic performance of specimens under water-saturated conditions during the water loss process.

Plastic shrinkage of mortars cured with a paraffin-based compound – Bimodal neutron/X-ray tomography study

Early-age drying (immediately after casting) of mortars and the corresponding plastic shrinkage were studied using bimodal neutron/X-ray computed tomography. This novel, correlative 3D imaging mode enabled studying simultaneously and without any source of spurious perturbation the water migration and loss processes together with the corresponding deformations due to plastic shrinkage. Bimodal imaging opens up new possibilities for studying dynamic processes of coupled water transport and deformations in porous solids. The measurements were carried out on model systems (cylindrical mortar specimens with height of 19 mm). The study focused on the effect of a paraffin-based curing compound. Our results confirm that when the curing compound was applied directly onto the drying surface in a sufficient amount, both the evaporation rate and the rate of vertical displacement (settlement) were substantially reduced. The results shed a new light on the mechanisms of plastic shrinkage and the action of curing compounds.

Особливості водного режиму рослин роду Clematis L.

Clematis is a medicinal plant and a promising culture for introduction into urbophytocenoses. In order to ensure optimal growing conditions, it is necessary to take into account the ecological needs of plants, a key place among which is water supply. The experiments were carried out with cultivars and species of the genus Clematis: Clematis alpina ‘Pamela Jackman’, C. macropetala ‘Maidwell Hall’, C. integrifolia ‘Aljonushka’, C. ispahanica ‘Zvezdograd’, C. fargesii ‘Paul Farges’, C. taxensis ‘Princess Diana’, C. tibetana, C. viticella and C. heracleifolia. Ecological peculiarities of studied plants cause differences in the anatomical tissues structure and dynamic of physiological processes. The lowest content of dry matter in the leaves was found in C. alpina ‘Pamela Jackman’ (16,3 %) and C. macropetala ‘Maidwell Hall’ (18,3), indicating their potentially lowest drought resistance. The highest value of this index was identified in C. heracleifolia (27.5 %) and C. integrifolia ‘Aljonushka’ (23.4 %), that characterizes them as the most drought resistant among studied plants. A function describing the process of cutted leaves wilting at the temperature +60 °C was defined: f(x) = y0 + ae–bx. A significant correlation was found between the parameter y0 and the dry mass (0.99), water content (0.86) in the leaves and their weight before drying (0.91); the parameter a and the mass index of leaves before wilting (0.99), the water content (1.00) and dry matter (0.83), as well as the density (0.86) and the area of stomatas (0.81) on the adaxial surface of leaves. Parameter b correlated with the values of dry mass (—0.75), its fraction in the total leaf mass (—0.84), the water fraction (0.83) and the width of spongy mesophyll cells (0.76). The peculiarities of anatomical structure and dynamic of leaves water loss process among investigated plants indicate the difference in their potential drought resistance. Obtained results allow to choose the optimal conditions for growing of investigated plants of the genus Clematis and planning additional care measures.

Detection and attribution of lake water loss in the semi‐arid Mongolian Plateau—A case study in the Lake Dalinor

AbstractExtensive lake shrinkages have been observed in the semi‐arid Mongolian Plateau over the past several decades, causing a great challenge to the local socio‐economic sustainability and ecological security. However, issue on the dominant drivers of this water loss has not been well addressed. In this work, variations in water area and water level of the Lake Dalinor during the period 1984–2018 were tracked using the satellite altimetry and Landsat images. Dominant drivers for the derived variations were then investigated based on the Standard Precipitation Evaporation Index (SPEI) analysis and the Vegetation Interface Processes model. Results showed that both the water area and water level displayed a two‐stage variation with a slightly increasing trend before 2000 and a drastic decline since 2000 (p &lt; 0.01). The SPEI analysis revealed a close relationship between water level variations and the cumulative water anomalies at seasonal and annual scales. The model‐based attribution analysis suggested that climate change and anthropogenic impacts contributed 76.5% and 23.5% of the observed declining trend, respectively. Climate warming and drying dominated the water level decline since 2000, while the large‐scale conversion from the natural grassland to the seeded pasture might have accelerated this water loss process. This study confirmed the prominent impacts of climate warming and drying on the lake desiccation in the semi‐arid Mongolian Plateau and highlighted the gradually intensifying impacts of human activities such as grassland conversion on the lake water budget.

Water Flow Behavior and Storage Potential of the Semi-Arid Ephemeral River System in the Mara Basin of Kenya

Alluvial corridors of ephemeral river systems provide viable opportunities for natural water storage in dry lands. Whilst alluvial corridors are widely recognized as water buffers, particularly for areas experiencing constant water scarcity, little research has been undertaken in Sub-Saharan Africa to explore their hydrological variability and water resource potential as alternative water sources for nearby communities. This study investigated the water flow behavior and storage potential of an ephemeral river system in the Mara Basin of Kenya for purposes of supporting water resources development and ecological sustainability. The water flow processes - including the recharge rates and water loss processes - from existing sand storage systems were established through monitoring of ground and surface water levels. Water samples along the alluvial corridor were collected and analyzed for major ions and isotopic signatures required to establish the water storage dynamics. The storage potential was estimated through Probing and Electrical Resistivity Tomography techniques, augmented with in-situ measurements of hydraulic conductivities and channel bed porosities. The mean annual storage volume in the alluvium of the study reach was estimated at 1.1 Mm3, potentially capable of providing for the annual domestic and livestock water demands of the area. Transmission losses into the alluvium beneath the ephemeral channel-bed were noted to attenuate the flood peak discharges, depending on the level of saturation of the alluvial bed. However, water storage in the alluvium was subject to losses through evapotranspiration and seepage through fractured bedrocks. The study demonstrated the potential of alluvial corridors as water storage buffers providing alternative water sources to communities within the dry land regions with water scarcity, thereby to supporting ecosystem sustainability.

Role of rock dip angle in runoff and soil erosion processes on dip/anti-dip slopes in a karst trough valley

Due to the great difficulty of monitoring surface and underground runoff and sediment yield directly, the surface and underground hydrological processes associated with soil leakage loss in karst trough valleys remain unknown. The objective of this study was to analyse the role of the rock dip angle in the water and soil leakage loss processes, to assess the characteristics of surface and underground runoff and soil erosion and to investigate their conversion relationships using rainfall experiments. The results showed the following. i) At a steep rock dip angle (60°), the underground runoff yield had a shorter stabilization time than the surface runoff yield and that the underground runoff coefficient of the dip slope exceeded 0.5. ii) The surface sediment yield could be divided into the suspended load and the bed load and the underground sediment yield included only the suspended load. On the anti-dip slope, the surface erosion modulus was 0.83–2.50 times the underground erosion modulus. iii) The surface and underground cumulative runoff was linearly correlated with the cumulative sediment yield. The rock dip angle had a significant quadratic relationship with the surface and underground runoff and sediment yield. These results improve the understanding of the surface-underground runoff and soil erosion processes and have significance for preventing water and soil leakage loss on the slopes of karst trough valleys.

The numerical simulation of Influence of Drying-wetting Cycles on the Deterioration Characteristics of Gypsum Rocks under Particle Flow Code

In order to study the influence of dry-wet cycling on the deterioration characteristics of gypsum rocks and solve the problems encountered in engineering construction, in this study, gypsum rocks are taken as the research object. With the combination of laboratory test and theoretical analysis, the numerical simulation of particle flow is carried out, and the deterioration characteristics of physical and mechanical properties of gypsum rock under dry-wet cycling are studied. The results show that gypsum, quartz, zeolite and dolomite are the main components of gypsum rocks. Gypsum occupies the most components in gypsum rocks, so the various characteristics of gypsum greatly affect the characteristics of gypsum rocks. The process of water absorption and loss of gypsum is similar, which shows that the rate of water absorption or loss of gypsum is faster in the early stage, and tends to be stable in the later stage. The curve of the whole process of water absorption and loss is fitted by negative exponential function, and the effect is better. The larger the porosity of gypsum rock is, the better its water absorption performance is. Intergranular pore, dissolution pore and dissolution pore are the main pore types of gypsum rock. Intergranular pore is the main water absorption channel of gypsum rock. The cumulative water absorption increases with the increase of wetting and drying cycles. The change of water absorption curve is mainly manifested in water absorption rate and time. The more the number of wet-dry cycles is, the higher the water absorption rate in the early stage of water absorption is, the closer the characteristic curve to the coordinate axis of water absorption is, and the shorter the water absorption time is. In contrast, the shape difference of water loss curve is very small. It can be seen from this that in the process of wetting and drying cycle, the hydrophysical and hydrochemical processes promote each other, which changes the crystal structure and pore structure of gypsum rocks, reduces the crystal strength and increases the porosity, thus leading to the deterioration of the mechanical properties of gypsum rocks.