Inflow Discharge Research Articles

Experimental Investigation on the Breaching Process of Landslide Dams with Differing Materials under Different Inflow Conditions.

Landslide dams are dangerous because the outburst floods produced by dam failures seriously threaten life and property downstream. In this study, a series of physical flume tests were conducted to investigate the breaching process of landslide dams with fine-grained, well graded, and coarse-grained material under different inflow conditions. The effects of dam material and inflow discharge on the breach development, outflow discharge and erosion characteristics were studied. The erosion resistance of materials and lateral collapses were also discussed. Experimental results reveal that the whole breaching process is determined by the water-sediment interaction. For the fine-grained dams, a general constant downstream slope angle is maintained during the breaching process. For the well-graded dams, a step-pool structure is generated due to the scarp erosion. For the coarse-grained dams, they can remain stable under normal circumstances but fail by overtopping in a short duration under the extreme inflow condition. The final breach of the dam with higher fine content or larger inflow discharge is deeper and narrower. In addition, many fluctuations are observed in the changing curve of the erosion rates along the flow direction for the well-graded and coarse-grained dams. The erosion resistance of materials increases along the flow direction, which needs to be further considered in physically based breach models. Furthermore, the lateral collapse is affected by the dam material instead of inflow discharge. The lower fine content causes more lateral collapses with smaller volumes.

Variability of Discharge Inflow in Wonorejo Reservoir, Indonesia

Discharge variability such as frequency and magnitude at certain seasons has the main control on the hydrological behavior of the river. This means a better understanding of discharge variability for reservoir inflow it can be used to manage water reservoir manajement more effectively during the wet year we can use more water, and during the dry season water saving must be done. This flow discharge variation was investigated using data for 18 years from 2003 to 2020 using data on the daily inflow gate of the Wonorejo Reservoir. This study was used to examine the Standardized Precipitation Index (SPI) and statistical methods in the form of average annual discharge, standard deviation (SD), and coefficient of variation (CV) were used to determine the relationship between rain and discharge that occurred. The results of this study show the variability of the discharge for wet, normal and dry years, as well as the distribution of, and changes in the stream flow record. This study is very valuable in order to know the trend of seasonal discharge that occurs, the estimated highest and lowest discharge, as well as the annual discharge cycle in the context of water resources management. Thus, the inflow discharge of the Wonorejo Reservoir from January 2003 to December 2020 shows that each time series follows a normal distribution with a probability percentage of a wet year and a dry year of 41% while a normal year is 11%.

A novel lake-zoning framework for large lakes based on numerical modelling

Because of the high spatial heterogeneity of the ecosystem properties of large lakes, the characterisation of lake zones is particularly helpful for designing zone-specific strategies for water management practices. In this study, we developed a lake-zoning framework by investigating the lateral dispersion of inflow pollutants through dye-tracking experiments in a case study of a large shallow lake (Lake Chaohu) in China. A two-dimensional hydrodynamic and mass transport model was used to quantify the impacts of inflow rivers on this lake. Results from 2012 to 2014 showed that the lake zoning results were more stable at the annual scale than at the seasonal scale, implying that the seasonal scale is not suitable for the establishment of lake zones. A driving factor analysis showed that inflow discharge was a more critical factor determining lake zones than wind conditions. In contrast to previous lake zoning methods, the proposed framework implements lake zoning quantitatively through hydrodynamic modelling.

An effective alternative for predicting coastal floodplain inundation by considering rainfall, storm surge, and downstream topographic characteristics

The extent of coastal flooding is influenced by many factors such as the topography of the low-lying land, tidal level, rainfall pattern, inflow discharge collected from the upstream drainage area, etc. This study establishes a new methodology of effectively predicting the flooding process in coastal areas, and which is achieved by combining the recurrent neural network (RNN) model with the detailed analysis of different hydrological and geomorphological factors. The novelty of this study is to apply the topographic wetness index (TWI) of each grid to classify all inputs into multiple classes for separative training to improve the overall accuracy of flooding simulations. A numerical inundation model based on hydrodynamic equations was applied to investigate the behavior of coastal flooding in the temporal and spatial domain under a variety of model settings with different hydrologic conditions and it was utilized to generate the target inundation depths for the training of the RNN model. The relevance between the downstream topography, tidal level, rainfall intensity, and the spatial distribution of flooding in coastal areas is explored via the use of machine learning (ML) techniques. The focus of this study is to evaluate the proposed alternative method that allows for improving the efficiency and stability of forecasting coastal floods caused by rains and storm surges due to the approaching tropical cyclones. The method developed in this study is promising to replace the numerical inundation model to reinforce the model’s stability and computational efficiency.

Improvement of Flood Extent Representation With Remote Sensing Data and Data Assimilation

Flood simulation and forecast capability have been greatly improved thanks to advances in data assimilation. Such an approach combines in-situ gauge measurements with numerical hydrodynamic models to correct the hydraulic states and reduce the uncertainties in the model parameters. However, these methods depend strongly on the availability and quality of observations, thus necessitating other data sources to improve the flood simulation and forecast performances. Using Sentinel-1 images, a flood extent mapping method was carried out by applying a Random Forest algorithm trained on past flood events using manually delineated flood maps. The study area concerns a 50-km reach of the Garonne Marmandaise catchment. Two recent flood events are simulated in analysis and forecast modes, with a +24h lead time. This study demonstrates the merits of using SAR-derived flood extent maps to validate and improve the forecast results based on hydrodynamic numerical models with Telemac2D-EnKF. Quantitative 1D and 2D metrics were computed to assess water level time-series and flood extents between the simulations and observations. It was shown that the free run experiment without DA under-estimates flooding. On the other hand, the validation of DA results with respect to independent SAR-derived flood extent allows to diagnose a model-observation bias that leads to over-flooding. Once this bias is taken into account, DA provides a sequential correction of area-based friction coefficients and inflow discharge, yielding a better flood extent representation. This study paves the way towards a reliable solution for flood forecasting over poorly gauged catchments, thanks to available remote sensing datasets.

Analysis and evaluation of flood routing using Muskingum method

There are several mathematical procedures that deal with hydrologic flood routing. The Muskingum technique is one of the most common techniques used for flood routing for river reach. From the hydrologic point of view, flood routing in a stream is used to predict the flood discharge, or storage, at any downstream station in a stream channel from a known discharge, or stage, at an upstream station. Hydrologic routing is an approximate technique. However, it provides relatively easy alternative, for solving flood routing problems. It is based on the storage and the continuity equations. In principle hydrologic routing employs historical data on inflow and outflow discharges in the reach under study. The Muskingum method is the particular one to be considered in this paper, describing three procedures, other than the classical trial and error procedure, for solving flood routing.

Analysis of the role of long-term and short-term periods of inflow in reservoirs water resources planning

Predicting of inflow discharge to reservoir dams is very important in achieving the purposes of reservoirs water planning. Due to climate change and human activities in the upstream of basins in recent years, the time series of discharge data has generally had downward trend. Therefore, estimating of the discharge in different statistical periods (long-term, medium-term and short-term) and analyzing it in the selection of project purposes has undeniable importance. In this study, the estimate of inflow discharge in 4 dams located in East Azerbaijan province (northwest of Iran) in different statistical periods was performed, and the effect of selecting each statistical period in the dams water resources planning was analyzed. The results showed that depending on the conditions of each basin, the selection of the appropriate discharge period will be different. But in general, choosing a short period of 15-20 years is appropriate and effective in achieving the goals of the project.

Variation in soil detachment capacity of structural and sedimentary crusts induced by simulated rainfall formed on ridge and furrow

The response of erosion to soil physical crusts (i.e., structural and sedimentary crusts) has been extensively investigated. Yet few studies have quantified the effects of physical crusts on their detachment capacity (Dc). Accordingly, we investigated the variation in Dc of physical crusts as induced by simulated rainfall. The runoff plot (2.0 m long × 1.0 m wide × 0.5 m high) was set to a slope of 5° and filled with Lou soil (Haplic Luvisol) using horizontal tillage with ridges (1.0 m long × 0.2 m wide × 0.1 m high) and cm furrows (1.0 m long × 0.3 m wide × 0.1 m deep). Simulated rainfall was applied at a single intensity (60 mm h−1) for seven durations (0, 5, 10, 15, 20, 25, and 30 min) to obtain structural (at ridges) and sedimentary (at furrows) crusts. Crust samples were collected to obtain Dc, by scouring them for 2 min at a constant inflow discharge (0.8 L min−1) on a hydraulic flume (15° slope). For both structural and sedimentary crusts, with increasing rainfall duration, the measured bulk density (BD), crust thickness (Ct), micro-aggregate content (MIA), and disintegration index (DI) increased, whereas the macro-aggregate content (MAA) decreased. Dc of 0 min and structural crust formed within 5 min of rainfall decreased with a longer scouring time. By contrast, Dc of the other crust types initially rose with an extended scouring time but then plateaued after ∼ 60 s. Dc of sedimentary crusts were significantly lower than that of structural crusts. Notably, crusts formed by rainfall at 30 min had greatest detachment reduction benefit. Dc was inversely related to BD, Ct, MIA and DI, whereas increased with increasing MAA. This research provides a timely reference for the effect of physical crust on concentrated flow in arid and semi-arid areas.

Physical modelling of energy losses at surcharged three-way junction manholes in drainage system.

Motivated by the observation that vortex flow structure was evident in the energy loss at the surcharged junction manhole due to changes of hydraulic and geometrical parameters, a physical model was used to calculate energy loss coefficients and investigate the relationship between flow structure and energy loss at the surcharged three-way junction manhole. The effects of the flow discharge ratio, the connected angle between two inflow pipes, the manhole geometry, and the downstream water depth on the energy loss were analyzed based on the quantified energy loss coefficients and the identified flow structure. Moreover, two empirical formulae for head loss coefficients were validated by the experimental data. Results indicate that the effect of flow discharge ratio and connected angle are significant, while the effect of downstream water depth is not obvious. With the increase of the lateral inflow discharge, the flow velocity distribution and vortex structure are both enhanced. It is also found that a circular manhole can reduce local energy loss when compared to a square manhole. In addition, the tested empirical formulae can reproduce the trend of total head loss coefficient.

Identifying key drivers of harmful algal blooms in a tributary of the Three Gorges Reservoir between different seasons: Causality based on data-driven methods

Intense harmful algal blooms (HABs) can occur in the backwaters of tributaries supplying large-scale reservoirs. Due to the characteristics of process-based models and difficulties in modelling complex nonlinear processes, traditional models have difficulties disentangling the driving factors of HABs. In this study, we used data-driven methods (i.e., correlation analysis and machine-learning models) to identify the most important drivers of HABs in the Xiangxi River, a tributary of the Three Gorges Reservoir, China (2017–2018), for the dry season (from October to mid-April) and wet season (from April to September). We utilized the maximal information coefficient (MIC) combined with a time lag strategy and prior knowledge to quantitatively identify the driving variables of HABs. An extra trees regression (ETR) model was developed to assess the relative importance of causal variables driving algal blooms for the different periods. The results showed that water temperature was the most important driver for the duration of the study, followed by total nitrogen. Nitrogen had a stronger effect on algal blooms than phosphorus during both the wet and dry seasons. HABs were mainly affected by ammonia nitrogen in the wet season and by other forms of nitrogen in the dry season. In contrast, rather than the water temperature and nutrients, the operation of the Three Gorges Dam (difference between inflow and outflow discharge rate) was the most significant factor for algal blooms during the dry season, but its influence sharply declined during the wet season. This study showed that the key drivers of HABs can differ between seasons and suggests that HAB management should take seasonality into account.

A Three-Dimensional Coupled Hydrodynamic-Ecological Modeling to Assess the Planktonic Biomass in a Subalpine Lake

In this study, a coupled three-dimensional hydrodynamic-ecological model was developed to comprehensively understand the interaction between the hydrodynamics and ecological status of a lake. The coupled model was utilized to explore the hydrodynamics, water quality, and ecological status in an ecologically rich subalpine lake (i.e., Tsuei-Feng Lake (TFL), located in north-central Taiwan). The measured data of water depth, water temperature, water quality, and planktonic biomass were gathered to validate the coupled model. The simulated results with a three-dimensional hydrodynamic and water quality-ecological model reasonably reproduced the variations in observed water depth, water temperature, water quality, and phytoplankton and zooplankton biomass. Sensitivity analysis was implemented to determine the most influential parameter affecting the planktonic biomass. The results of sensitivity analysis indicated that the predation rate on phytoplankton (PRP) significantly affects the phytoplankton biomass, while the basal metabolism rate of zooplankton (BMZ) importantly affects the zooplankton biomass. Furthermore, inflow discharge was the most important environmental factor dominating the phytoplankton and zooplankton biomass of TFL. This implies that the runoff in the catchment area caused by rainfall and the heavy rainfall induced by climate change may affect the planktonic biomass of the lake.

Combined effects of rainfall and flow depth on the resistance characteristics of sheet flow on gentle slopes

Rainfall and sheet flow (SF) on gentle slopes always appear concurrently. However, the combined effects of rainfall and flow depth on SF resistance are still unclear for gentle slopes. In this study, two sets of experiments, namely, upstream inflow with rainfall and upstream inflow only, were conducted to investigate the resistance characteristics of SF on a flat and smooth flume with three gentle slopes (3°, 5° and 7°). The experimental results indicated that in the tests with upstream inflow only, the Darcy–Weisbach resistance (f) and Manning coefficient (n) decreased following a power function with increasing flow depth. When the Reynolds number (Re) was less than 1070, the n and f of the SF in the upstream inflow alone decreased with increasing Re following the power function. Both the n and f of the SF increased with increasing rainfall intensity for the upstream inflow with the rainfall tests. The rainfall significantly affected the f and n of the SF in the low Re zone (Re < 1070), inflow discharge (<0.06 m2 min−1) and flow energy for all inflow with rainfall cases. Under the conditions of upstream inflow with rainfall, both the f and n of the SF decreased with the increase in the ratio between the flow depth and median raindrop diameter (H/D50) in the power function. This result indicated that a deeper flow could dissipate more raindrop energy. In addition, empirical equations among Re, hydraulic slope and H/D50 were established to predict the n and f of the SF for upstream inflow with rainfall tests. This study will be helpful in understanding the combined effects of rainfall and flow depth on SF and could provide a scientific basis for improving hydrological and soil erosion models.

Experimental Investigation of the Outburst Discharge of Landslide Dam Overtopping Failure

Research on the factors and mechanisms that influence outburst floods are essential for estimating outflow hydrographs and the resulting inundation. In this study, large flume tests are conducted to investigate the effects of the upstream inflow and the presence of loose erodible deposits on the breaching flow and the subsequent outburst floods. Experimental results reveal that hydrographs of the breaching flow and outburst flood can be divided into three stages where each stage is separated by inflection points and peak discharges. It is found that the larger the inflow discharge, the larger the peak discharge of the outburst flood and the shorter the time needed to reach the peak and inflection discharges of the outburst flood. The breaching flow decreases along the longitudinal direction at rates that increase with the inflow discharge. The ratio between the length of the upstream dam shoulder and the dam width is inversely related to the ratio of the outburst discharge to inflow discharge. We also show that the presence of loose deposits at the dam toe can amplify the peak discharge of outburst flood by increasing the solids content of the water flow.

NUMERICAL STUDY ON SUSPENDED SEDIMENT TRANSPORT UNDER THE EFFECT OF WATER TEMPERATURE IN RESERVOIRS/LAKES

Water resources management is one of the most important issues and challenges in the world. This management may be in the form of quality management or quantitative management of water resources. Quality management of water resources is of great importance. A major problem in this case is how the input flow (for example a river) will behave when water flows to a dam reservoir or lake. Distribution of the input stream to the reservoir/lake depends on important parameters such as inflow discharge, input depth, situation and type of the reservoir outlet, type of inlet sediment , sediment concentration of inflow current and reservoir/lake , and etc. Therefore, this effect of each of the mentioned parameters on the distribution in the reservoir or lake should be examined. An important parameter that has not yet been studied is the effect of temperature of the inflow current's and the reservoir/lake's water on the distribution. For this purpose, the FLOW3D computational fluid dynamics code was selected in this study. The effect of water temperature and concentration of suspended sediment on distribution in reservoirs/lakes is considered. Several simulations with different water temperature and suspended sediment concentration values were done. Results are shown and compared each other. The results indicate the high effect of water temperature on distribution of sediments.

Geochemistry of the redox-sensitive trace elements molybdenum, tungsten, and rhenium in the euxinic porewaters and bottom sediments of the Pettaquamscutt River estuary, Rhode Island

Molybdenum (Mo), tungsten (W), and rhenium (Re) concentrations were measured in the porewaters and sediments of the highly stratified Upper Basin of the Pettaquamscutt River estuary (Rhode Island) to investigate the geochemical processes that influence their concentrations in euxinic systems. Total dissolved sulfide (i.e., ΣS-II) concentrations in the porewaters averaged 3.95 mmol kg−1, whereas the porewaters exhibited average Mo, W, and Re concentrations of 830 nmol kg−1, 69 nmol kg−1, and 7.4 nmol kg−1, respectively. The sediments were subjected to chemical extractions to characterize the reactive fraction (i.e., associated with iron (Fe) monosulfides, Fe/manganese (Mn) oxides/oxyhydroxides, and/or Fe/Mn carbonate minerals) and the pyritized fraction of Mo, W, and Re in the sediments. The reactive fraction of each metal decreased with depth from subsurface maxima near the sediment-water interface, whereas the pyritized fractions exhibited a number of subsurface maxima. Rhenium exhibited the greatest degree of trace metal pyritization (DTMP) in the estuary sediments, followed closely by Mo. Specifically, the DTMP for Re ranged from 75 to 88% and exhibited a mean ( ± 1σ) of 80 ± 4% for the entire sediment core, whereas the DTMP for Mo ranged from 34 to 89% with a mean ( ± 1σ) of 73 ± 18%. In contrast, the DTMP for W was lower, ranging from 48 to 73%, but with a mean ( ± 1σ) of 58 ± 8%. Therefore, about 80%, on average, of the Re and 74% of the Mo that enters the northern portion of the Pettaquamscutt River estuary by the combination of stream water inflow (i.e., Gilbert Stuart Stream) and submarine groundwater discharge (SGD) is eventually fixed within the pyrite fraction of the euxinic bottom sediments. However, only about 60% of the W appears to be fixed in the pyrite fraction in these sediments, whereas the other 40% remains in the reactive sediment pool. We suggest that the different behavior of W compared to Re and Mo in the euxinic porewater and sediments of the Pettaquamscutt River estuary's upper basin reflects, in part, differences in their aqueous speciation and particle reactivity that appears to be dictated by differential uptake and fixation of their respective thioanions (i.e., MoS42−, WS42−, ReS4−) with Fe sulfide minerals.

Coastal town flooding upon compound rainfall-wave overtopping-storm surge during extreme tropical cyclones in Hong Kong

Study regionHong Kong, China. Study focusThis paper aims to develop a flood analysis model to integrate the effects of multiple flooding triggers (i.e. rainfall, high sea levels and wave overtopping) during powerful tropical cyclones and investigate coastal flood hazards in an urban area at the street scale. The process of wave overtopping is properly estimated and integrated in a dual-drainage model in a maneuverable way as an inflow discharge hydrograph. The inundation during Typhoon Mangkhut, 2018, in Tseung Kwan O town center, a coastal community of Hong Kong, is taken as a case study. New hydrological insights for the regionThe inundation scenario in Tseung Kwan O town center during Tyhpoon Mangkhut is reproduced and comparison between different drainage conditions demonstrates the key role of drainage facilities in the mitigation of flooding induced by wave overtopping, although the varying sea level boundary could partly reduce the drainage efficiency. In addition, possible flood scenarios and pedestrian stability in flowing water upon the unfavorable combination of storm surge and astronomical tide, as well as the effectiveness of a 1.1 m wave wall are evaluated. The overtopping discharge, flooding severity and dangerous zones for pedestrian can be markedly reduced by the wave wall.

Conceptualizing a multi‐layered shingle aquifer model based on volcanic stratigraphy and water inflow to lava caves in Jeju Island, Korea

AbstractVolcanic aquifers supply a substantial portion of water resources in many parts of the world, including islands, and their productivity depends strongly on volcanic stratigraphy, which exhibits considerable heterogeneity. We investigated water inflow to lava tube caves formed from numerous basaltic lava flows in the northeastern coastal area of Jeju Island after storm events and monitored relative inflow rates monthly over 1 year to characterize groundwater flow processes in the upper parts of volcanic aquifers, and to evaluate the applicability of the previous hydrogeological models proposed for the island. Considerable water inflow arose shortly after storms from exposed palaeosol layers on the walls of the caves. The monthly monitoring results showed that wall inflow associated with these palaeosol layers is substantial. In both cases, discharge from ceiling drips was much less and more temporally variable compared to wall inflow discharge. Water flowing into the caves was rapidly drained through the floor at all monitoring sites. The lateral extent of the palaeosol layers was identified using drill core logs near the cave and outcrops in the coastal area. Based on these results, we inferred that multiple perched aquifers are formed by low‐permeability palaeosol layers between lava flows, which are connected by vertical flows at discontinuities in the palaeosol layer, eventually reaching the basal aquifer. This study revealed the water inflow processes observed in lava tube caves constrained by palaeosol layers, and established a hydrogeological conceptual model incorporating multiple perched aquifers in both coastal and mountainous areas associated with extensive palaeosol layers formed during volcanic hiatuses. This finding would help elucidate recharge, groundwater flow, and contaminant transport processes in many volcanic aquifers that are not adequately represented by the previous models, and contribute to better management of groundwater in those areas.

Laboratory study of the effects of flexible vegetation on solute diffusion in unidirectional flow

BackgroundFlexible vegetation is an important part of the riverine ecosystem, which can reduce flow velocity, change turbulence structure, and affect the processes of solute transport. Compared with the flow with rigid vegetation, which has been reported in many previous studies, bending of flexible vegetation increases the complexity of the flow–vegetation–solute interactions. In this study, laboratory experiments are carried out to investigate the influence of flexible vegetation on solute transport, and methods for estimating the lateral and longitudinal diffusion coefficients in the rigid vegetated flow are examined for their applications to the flow with flexible vegetation.ResultsThe experimental observations find that vegetation can significantly reduce flow velocity, and the Manning coefficient increases with increasing vegetation density and decreases with inflow discharge. Under all the cases, the vertical peak of the solute concentration moves towards the bottom bed along the flow, and the values of vertical peak concentration longitudinally decreases from the injection point. The lateral diffusion coefficients Dy increase with vegetation density, while the longitudinal diffusion coefficients DL are opposite. Both Dy and DL increase with the inflow discharge. To estimate the Dy and DL in the flow with flexible vegetation, an effective submerged vegetation height considering vegetation bending is incorporated in the methods proposed for flow with rigid vegetation (Lou et al. Environ Sci Eur 32:15, 2020). The modified approach can well predict the diffusion coefficients in the experiments with the relative errors in the range of 5%–12%.ConclusionsThe methods proposed in this study can be used to estimate the lateral and longitudinal diffusion coefficients in flows through both rigid and flexible vegetations using the effective submerged vegetation height.

Erosion Rate of Lateral Slope Deposit Under the Effects of Different Influencing Factors

Lateral slope deposits along a channel represent an important source of material for initiation and development of debris flows/floods that are typically observed in many headwater tributaries. This study found that the failure process of such a deposit reflects combined interaction between external hydrodynamic factors (inflow discharge and channel slope) and internal factors (compactness and fine particle content). The erosion process comprises two stages: runoff erosion toward the toe of the deposit body and soil failure owing to gravity. Spatially, the erosion rate is distributed unevenly across the deposit; the highest value occurs at the section close to the middle of the deposit, on the upstream face. Temporally, the erosion rate decreases exponentially. Overall, the average erosion rate decreases (increases) with bulk density (inflow discharge and channel slope). However, a slope of 7 is a threshold at which the tendency of the erosion rate in relation to the fine particle content differs. In comparison with the other three influencing factors, the effect of the fine particle content is much smaller. Although the bulk density of the deposit imposes the most significant effect, it is of the same order as that of both inflow discharge and channel slope. As the failure process can be summarized as repeated runoff scouring of the toe of the deposit, deposit failure, and entrainment of the failure body by runoff, we proposed a calculation method for the total time required for a complete lateral erosion process, and validation of the calculation suggested its reasonability. The findings of this study enhance the understanding of the mechanism of lateral soil deposit failure, which could help improve runoff-induced debris flood forecasting in headwater regions of mountainous catchments.

Simulating advance distance in border irrigation systems based on the improved method of characteristics

Improving the simulation accuracy of the advance distance based on the method of characteristics is essential to develop numerical solutions for simulating surface irrigation. Instead of volume balance in the traditional method of characteristics (T-MC), the position of critical flow is determined to simulate the advance distance in the improved method of characteristics (I-MC), which is used in border irrigation systems with rapid variation in inflow discharge in the current research. Specifically, the zones of both subcritical and supercritical flow were firstly distinguished to determine the position of the critical flow point, which was also the upstream boundary of the wetting front region, and then the advance distance was calculated by applying the diffusive wave equation in the wetting front region. The results showed that the I-MC accurately simulated the advance distance with high determination coefficients (0.984-0.998) and low errors (root mean square error of 0.35-1.56 min and coefficient of residual mass of 0.01-0.06), which performed much better than the T-MC. The I-MC provided a suitable and simple numerical simulation tool to improve the establishment of numerical surface irrigation models. Keywords: border irrigation, numerical solution, advance distance, method of characteristics DOI: 10.25165/j.ijabe.20211403.5877 Citation: Liu K H, Jiao X Y, Guo W H, Salahou M K, Gu Z. Simulating advance distance in border irrigation systems based on the improved method of characteristics. Int J Agric & Biol Eng, 2021; 14(3): 156–162.