Physical Catchment Characteristics Research Articles

Effect of watershed characteristics on river flow for the case of two watersheds, Megech and Gumaro, Upper Blue Nile Basin, Ethiopia

Land degradation is a series of problems in Ethiopia’s highlands, particularly in the Upper Blue Nile River Basin reflected in the form of soil erosion and reduce soil fertility from time to time. The effect of watershed characteristics on the river flow of those watersheds was evaluated by distributing a physically based hydrological model known as the soil and water assessment tool model. The model was calibrated for the river flow from 1992 to 2006 and validated for the period from 2007 to 2014. The performance of the model was evaluated based on performance rating criteria, coefficient of determination, and Nash and Sutcliff efficiency on monthly based value, the coefficient of determination (R2) and Nash–Sutcliffe coefficient was greater than 0.6 and 0.5 for all scenarios on both watersheds, respectively. The land-use land-cover change scenario, the climate characteristics, and the slope change scenario was developed, from those analyses, it was found that has been a substantial decrease or increase in forest land, shrubland, grassland, and expansion of agricultural land. The mean annual streamflow of 2010 LULC decreased by 1.44% for 2010 from 2003 LULC and 5.23% for 2018 from 2010. Because of reduced cultivated land from 2010 up to 2018 and increased grassland and plantation in the Megech watershed and 2010 LULC decreased by 0.9% for 2010 from 2003 LULC and 2.04% in 2018 from 2010. This distributed physically based hydrological model has been applied for the evaluation of physical catchment characteristics with significant differences which was Cropland for Megech and Gumaro watersheds which were 67.28% and 61.5%, respectively, for the 2003 LULC, 64.94% Megech, and 58.89% for Gumaro watershed for 2010LULC and 51.95% for Megech and 42.12% for Gumaro watershed, similarly, Eutric Cambisols were covering large areas for both watersheds.

Hydrological Drought Assessment in a Small Lowland Catchment in Croatia

Hydrological drought is critical from both water management and ecological perspectives. Depending on its hydrological and physical features, the resilience level of a catchment to groundwater drought can differ from that of meteorological drought. This study presents a comparison of hydrological and meteorological drought indices based on groundwater levels from 1987 to 2018. A small catchment area in Croatia, consisting of two sub-catchments with a continental climate and minimum land-use changes during the observed period, was studied. The first analysis was made on a comparison of standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI). The results showed their very high correlation. The correlation between the standardized precipitation index (SPI) and standardized groundwater index (SGI) of different time scales (1, 3, 6, 12, 24 and 48 months) showed different values, but had the highest value in the longest time scale, 48 months, for all observation wells. Nevertheless, the behavior of the SPI and groundwater levels (GW) correlation showed results more related to physical catchment characteristics. The results showed that groundwater drought indices, such as SGI, should be applied judiciously because of their sensitivity to geographical, geomorphological, and topographical catchment characteristics, even in small catchment areas.

Storylines of UK drought based on the 2010–2012 event

Abstract. Spatially extensive multi-year hydrological droughts cause significant environmental stress. The UK is expected to remain vulnerable to future multi-year droughts under climate change. Existing approaches to quantify hydrological impacts of climate change often rely solely on global climate model (GCM) projections following different emission scenarios. This may miss out low-probability events with significant impacts. As a means of exploring such events, physical climate storyline approaches aim to quantify physically coherent articulations of how observed events could hypothetically have unfolded in alternative ways. This study uses the 2010–2012 drought, the most recent period of severe hydrological drought in the UK, as a basis and analyses storylines based on changes to (1) precondition severity, (2) temporal drought sequence, and (3) climate change. Evidence from multiple storylines shows that the maximum intensity, mean deficit, and duration of the 2010–2012 drought were highly influenced by its meteorological preconditions prior to drought inception, particularly for northern catchments at shorter timescales. The influence of progressively drier preconditions reflects both the spatial variation in drought preconditions and the role of physical catchment characteristics, particularly hydrogeology in the propagation of multi-year droughts. There are two plausible storylines of an additional dry year with dry winter conditions repeated either before the observed drought or replacing the observed dramatic drought termination confirm the vulnerability of UK catchments to a “third dry winter” storyline. Applying the UKCP18 climate projections, we find that drought conditions worsen with global warming with a mitigation of drought conditions by wetter winters in northern catchments at high warming levels. Comparison of the storylines with a benchmark drought (1975–1976) and a protracted multi-year drought (1989–1993) shows that, for each storyline (including the climate change storylines), drought conditions could have matched and exceeded those experienced during the past droughts at catchments across the UK, particularly for southern catchments. The construction of storylines based on observed events can complement existing methods to stress test UK catchments against plausible unrealised droughts.

The Impact of Rainfall -Runoff on the Performance of Main Irrigation Canal and Cross Drainage of Omo-Kuraz I and II Sugar Project (The Case of Omo-Gibe Basin)

Flood is serious economic losses like damage main irrigation canal and installed infrastructure on sugar project. The objective of this research was to provide an estimation of rainfall-runoff effect on main canal irrigation scheme. The hydrograph characteristics of observed and simulated events are compared using various evaluation criteria consisting of Nash-Sutcliffe coefficient (NSE) is between 0.8 and 0.9, relative volume error (RVE) between -10 and 10%, and coefficient of determination (r2) is between 0.8 and 0.9 during calibration and validation period. Among the catchments of the basin that are used in the regional modeling work and nine Model Parameters are selected among those commonly used in regionalization studies. Four parameter regionalization methods (linear regression, spatial proximity, area ratio and sub-basin mean) were applied to transfer model parameter values from the gauged to the un-gauged catchments except area ratio method. In regional model, gauged catchments Model Parameters and Physical catchment characteristics of un-gauged catchments were used to develop the equations in order to predict discharge of un-gauged catchments. To have better understanding of model parameter performance, the sensitivity analysis of nine model parameters were performed manually by trial and error. The evaluation demonstrations that time of concentration (TC), storage coefficient(R), maximum storage (MS) and constant rate (CR) are more sensitive than others. Therefore, spatial proximity method is recommended in predicting discharge for un-gauged catchments for this research and obtained 85.1m3/s, 1.6m3/s, 9m3/s, 0.6m3/s,1.1m3/s, 14.3m3/s and 28.2m3/s peak flow for cross drainage three, culvert outlet four, culvert outlet three, culvert outlet two, culvert outlet one, cross drainage thirteen and cross drainage fourteen un-gauged sub catchments respectively. To determined predicted peak discharge using L-moment method in flood frequency analysis of selected gauged catchment. Finally, flood damage protection structures like dyke must be recommended for temporary, but redesign depend on peak discharge is necessary. Keywords: HEC-HMS, Regionalization, Stream flow simulation, L-moment, un-gauged catchments, Omo-Gibe sub-basin DOI: 10.7176/CER/14-2-02 Publication date: April 30 th 2022

Hydrological seasonality and nutrient stoichiometry control dissolved organic matter characterization in a headwater stream

Dissolved organic matter (DOM) is a diverse and highly complex mixture of organic macromolecules, and thus plays a central role in aquatic ecosystems. However, responses of components and sources of DOM to hydrological processes and trophic levels (nutrient stoichiometric ratios) are poorly understood, particularly in monsoonal headwater streams of Asia that are vulnerable to catchment physical characteristics. In this study, the excitation - emission matrix florescence spectroscopy coupled with parallel factor analysis (EEM-PARAFAC) was used to explore the DOM characters in a headwater stream, where seasonal rainfalls and nutrient levels vary largely. The EEM-PARAFAC modelling identified one autochthonous protein-like fluorescence substance (C1) and two allochthonous fulvic- and humic-like fluorescence compounds (C2 and C3). The allochthonous compounds dominated the overall DOM signal in the headwaters. The hydrological seasonality coupled with nutrients was key in modulating headwater DOM sources and components. Seasonal rainfall events contributed more allochthonous terrestrial-derived DOM flushing into river waters, resulting in higher fulvic- and humic-like organic matter (C2 + C3) in the wet season. In the dry season, longer water residence time accompanying with higher C:P stoichiometric ratio was responsible for higher autochthonous microbial- and plant-derived DOM (tryptophan and tyrosine fractions), also reflected by higher C1, biological index (BIX) and freshness index (β:α). In-stream microbial metabolism of labile DOM fractions largely contributed to autochthonous DOM and partial pressure CO2 increase in the headwater stream. Our findings indicate that quality and quantity of DOM in headwater streams play a crucial role in downstream carbon cycle. Furthermore, the evidence combined from PARAFAC components, pCO2 and spectral slope clearly highlights the importance of microbial metabolism of carbon in lotic systems, especially during a dry season with increased residence time.

Generation of realistic synthetic catchments to explore fine continental surface processes

AbstractUnderstanding, analysing, and predicting the erosion mechanisms and sedimentary flows produced by catchments plays a key role in environmental conservation and restoration management and policies. Numerical case‐testing studies are generally undertaken to analyse the sensitivity of flood and soil erosion processes to the physical characteristics of catchments. Most analyses are conducted on simple virtual catchments with physical characteristics that, unlike real catchments, are perfectly controlled. Virtual catchments generally correspond to V‐shaped valley catchments. However, although these catchments are suitable for methodical analysis of the results, they do not provide a realistic representation of the spatial structures of the landscape and field conditions. They can, therefore, lead to potential modelling errors and can make it difficult to extend or generalize their results. Our proposed method bridges the gap between real and traditional virtual catchments by creating realistic virtual catchments with perfectly controllable physical characteristics. Our approach represents a real alternative to traditional test case procedures and provides a new framework for geomorphological and hydrological communities. It combines a field procedural generation approach, geographic information system processing procedures, and the CAESAR‐Lisflood landscape evolution model. We illustrate how each of these components acts in the process of generating virtual catchments. Five physical parameters were adjusted and tested for each virtual catchment: drainage density, hypsometric integral, mean slope of the main channel, granulometry, and land use. One of our virtual catchments is compared with a real catchment and a virtual catchment produced by a standard method. This comparison indicates that our approach can produce more realistic virtual catchments than those produced by more traditional methods, while a high degree of controllability is maintained. This new method of generating virtual catchments therefore offers significant research potential to identify the impacts of the physical characteristics of catchments on hydro‐sedimentary dynamics and responses.

Parameters Estimation at Ungauged Catchments Using Rainfall-Runoff Model, Upper Tekeze Basin, Ethiopia

This study was conducted for parametres estimation and stream flow prediction at ungauged catchments on the case of Upper Tekeze basin, Ethiopia by using Rainfall-runoff model. In the basin, most of the catchments were ungauged. The basin has 9199km2 and 3638km2 gauged and ungauged catchments respectively. Rainfall and stream flow data were analyzed in the period of 1992-2006 and 1992-20006, respectively. Parameters calibrated for gauged catchments were extrapolated to ungauged catchments on the base of similar physical catchment characteristics using regionalization techniques. Regionalization methods such as multiple linear regression, spatial proximity, sub basin mean and area ratio were applied to transfer model parameters values from gauged to ungauged catchments. For this study seven gauged catchments were satisfied objective functions in the calibrated and validation period, for example in Gheba catchment Nash-Sutcliffe model efficiency coefficient (NSE), relative volume error (RVE) and coefficient of determination (R2) were, 0.81, -4.25, 0.77 and 0.71, 5.5, 0.74 respectively. Stream flow simulation at ungauged catchments by using spatial proximity and sub basin mean method were contributing high runoff volume compare to other methods. The result for this study shows that the Key model parameters like runoff coefficient (Beta), recession coefficient of upper reservoir zone (Khq), Limit for evapotranspiration (Lp), field capacity (Fc), percolation (Perc) as defaulting value when applying HBV-96 model to the future regionalization studies. Model parameters were calibrated manually by try and error rules, however it was tidies therefore more creative automatic model calibration techniques could be useful for upcoming studies. Thus, Current and future water resources development endeavors may use apply such discharge data for planning and design purposes.

Towards natural water cycle in urban areas: Modelling stormwater management designs

ABSTRACT Urbanization modifies the natural water cycle particularly by reducing the water storage capacity. We analysed the storage capacity of three stormwater management designs in south-western Finland to demonstrate how an urban catchment releases stormwater and how storage contributes to flood resilience. The analysis relies on EPA SWMM5.1 simulations of water balance for a seven-month period including two extreme rain events during the summer and autumn. The enhanced storage capacity provided by the designs increased resilience against flooding and released stormwater with slower rates leading to reduced peak flows. Even the design with the least storage (10% LID coverage) was efficient at regulating floods due to controlled flow in a vegetated swale, whereas the design with the highest storage capacity (60% LID coverage) demonstrated the possibility of restoring nearly natural water cycle in urban catchments. The study suggests storage capacity can act as a flood resilience indicator directly linked with the physical catchment characteristics.

Intercontinental predictions of river hydraulic geometry from catchment physical characteristics

Hydraulic geometry is used to describe spatio-temporal variations in wetted width, mean depth and mean velocity with discharge in stream reaches. Models describing downstream (spatial variations) and at-a-station (temporal variations) hydraulic geometry are required for efficient and effective management of flow regimes, sediment and nutrient transport, and physical habitats at catchment to global scales. Data describing observed hydraulic conditions at 1327 stream reaches in France and New Zealand were compiled alongside reach descriptors and upstream catchments extracted from available GIS databases with nationwide coverage. Three contrasting empirical methods were developed to predict hydraulic geometry at unvisited sites. The first method applied basic models in which downstream hydraulic geometry parameters depend on discharge only. The second method applied separate country-specific models whose predictors were selected from the available nationwide GIS data from country. The third method applied an intercontinental model in which all observed hydraulic data were lumped together and predictors were selected from those available across both countries. Flexible regression models that account for interactions were used to parameterize second and third methods. Cross-validation tests showed that downstream parameters were well predicted for independent sites regardless of country. Model performance was higher for width than for depth. At-a-station parameters were less well predicted than downstream parameters, but the models provided satisfactory predictions of observed reach hydraulics. Importantly, the lumped intercontinental model performance was comparable to that of the country-specific models. This suggests that our approach can be applied in other regions where similar explanatory environmental variables are available.

Assessing multidecadal runoff (1970–2010) using regional hydrological modelling under data and water scarcity conditions in Peruvian Pacific catchments

AbstractIn a context of water scarcity in Peruvian Pacific catchments as a crucial issue for Peru, added to the paucity of data availability, we propose a methodology that provides new perspectives for freshwater availability estimation as a base reference for unimpaired conditions. Under those considerations, a regional discharge of 709 m3/s to the Pacific Ocean is estimated with a significant increasing trend of about 43 m3/s per decade over the 1970–2010 period.To represent the multidecadal behaviour of freshwater runoff along the region, a regional runoff analysis is proposed based on hydrological modelling at annual and monthly time step for unimpaired conditions over the whole 1970–2010 period. Differential Split‐Sample Tests are used to assess the hydrological modelling robustness of the GR1A and GR2M conceptual lumped models, showing a satisfactory transposability from dry to wet years inside the thresholds defined for Nash–Sutcliffe and bias criteria. This allowed relating physical catchment characteristics with calibrated and validated model parameters, thus offering a regional perspective for dryland conditions in the study area (e.g., the anticlockwise hysteresis relationship found for seasonal precipitation–runoff relationship) as well as the impacts of climate variability and catchment characteristics.

How does initial soil moisture influence the hydrological response? A case study from southern France

Abstract. The Cévennes–Vivarais region in southern France is prone to heavy rainfall that can lead to flash floods which are one of the most hazardous natural risks in Europe. The results of numerous studies show that besides rainfall and physical catchment characteristics the catchment's initial soil moisture also impacts the hydrological response to rain events. The aim of this paper is to analyze the relationship between catchment mean initial soil moisture θ̃ini and the hydrological response that is quantified using the event-based runoff coefficient ϕev in the two nested catchments of the Gazel (3.4 km2) and the Claduègne (43 km2). Thus, the objectives are twofold: (1) obtaining meaningful estimates of soil moisture at catchment scale from a dense network of in situ measurements and (2) using this estimate of θ̃ini to analyze its relation with ϕev calculated for many runoff events. A sampling setup including 45 permanently installed frequency domain reflectancy probes that continuously measure soil moisture at three depths is applied. Additionally, on-alert surface measurements at ≈10 locations in each one of 11 plots are conducted. Thus, catchment mean soil moisture can be confidently assessed with a standard error of the mean of ≤1.7 vol % over a wide range of soil moisture conditions. The ϕev is calculated from high-resolution discharge and precipitation data for several rain events with a cumulative precipitation Pcum ranging from less than 5 mm to more than 80 mm. Because of the high uncertainty of ϕev associated with the hydrograph separation method, ϕev is calculated with several methods, including graphical methods, digital filters and a tracer-based method. The results indicate that the hydrological response depends on θ̃ini: during dry conditions ϕev is consistently below 0.1, even for events with high and intense precipitation. Above a threshold of θ̃ini=34 vol % ϕev can reach values up to 0.99 but there is a high scatter. Some variability can be explained with a weak correlation of ϕev with Pcum and rain intensity, but a considerable part of the variability remains unexplained. It is concluded that threshold-based methods can be helpful to prevent overestimation of the hydrological response during dry catchment conditions. The impact of soil moisture on the hydrological response during wet catchment conditions, however, is still insufficiently understood and cannot be generalized based on the present results.

Decision‐Making and Flood Risk Uncertainty: Statistical Data Set Analysis for Flood Risk Assessment

AbstractFloods are a significant issue worldwide with over 1 billion people living in areas of potential flood risk. With climate change these risks are anticipated to increase, but there is great uncertainty associated with future projections, which poses challenges to those making decisions on flood management. Climate change projections which explicitly capture climate model parameters uncertainty are available in the United Kingdom; however, their use by practitioners, rather than researchers, has so far been limited. This paper takes an inclusive approach, working with end users, to answer practitioner relevant questions regarding future climate change influence for flood hazards. The method developed demonstrates the findings across Scotland, United Kingdom and investigates (i) the regional impacts to extreme flows and the associated uncertainty, (ii) the changes in extreme peak flows in terms of frequency, and (iii) the physical and hydroclimatic factors controlling these results. The method used industry standard statistical methods, driven by practitioner requirements, and explicitly includes the statistical uncertainty in the climate and extreme value distribution models in extreme flow estimates. Results are analyzed using hierarchical clustering and decision tree analysis, and the subsequent trends are shown to be constrained by different hydrological, climatic, and physical catchment characteristics. Results suggest that there is a high probability that low return period peak flow events would exceed the baseline extreme high return period event by the 2080s, which has significant implications for future‐proofing infrastructure design. This study provides a practical example and outputs resulting from collaboration between research and industry practices.

Land use affects total dissolved nitrogen and nitrate concentrations in tropical montane streams in Kenya

African tropical montane forests are facing fast and dynamic changes in land use. However, the impacts of these changes on stream water quality are understudied. This paper aims at assessing the effect of land use and physical catchment characteristics on stream water concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO3-N) and dissolved organic nitrogen (DON) in the Mau Forest, the largest tropical montane forest in Kenya. We conducted five synoptic stream water sampling campaigns at the outlets of 13–16 catchments dominated by either natural forest, smallholder agriculture or commercial tea and tree plantations. Our data show a strong effect of land use on TDN and NO3-N, with highest concentrations in stream water of catchments dominated by tea plantations (1.80±0.50 and 1.62±0.60mgNl−1, respectively), and lowest values in forested catchments (0.55±0.15 and 0.30±0.08mgNl−1, respectively). NO3-N concentration increased with stream temperature and specific discharge, but decreased with increasing catchment area. DOC concentrations increased with catchment area and precipitation and decreased with specific discharge, drainage density and topographic wetness index. Precipitation and specific discharge were also strong predictors for DON concentrations, with an additional small positive effect of tree cover. In summary, land use affects TDN and NO3-N concentrations in stream water in the Mau Forest region in Kenya, while DOC and DON were more related to hydrologic regimes and catchment properties. The importance of land use for NO3-N and TDN concentrations emphasizes the risk of increased nitrogen export along hydrological pathways caused by intensified land use and conversion of land to agricultural uses, which might result in deterioration of drinking water quality and eutrophication in surface water in tropical Africa.

Gully Head Retreat in the Sub‐Humid Ethiopian Highlands: The Ene‐Chilala Catchment

AbstractIn the northern highlands of Ethiopia, gully erosion is severe. Despite many efforts to implement gully prevention measures, controlling gully erosion remains a challenge. The objective is to better understand the regional gully erosion processes and to prevent gully head retreat. The study was conducted in the Ene‐Chilala catchment in the sub‐humid headwaters of the Birr River located southwest of Bahir Dar, Ethiopia. Twelve gully heads were monitored during the 2014 and 2015 rainy monsoon phase. We measured gully head morphology and retreat length, soil shear strength, ground water table levels, and catchment physical characteristics. Two active gully head cuts were treated in 2014 and an additional three head cuts in 2015 by regrading their slope to 45° and covering them with stone riprap. These treatments halted the gully head advance. The untreated gullies were actively eroding due to groundwater at shallow depths. The largest head retreat was 22.5 m, of which about half occurred in August of the first year when the surrounding soil was fully saturated. Lowering both the water table and protecting the gully heads can play a key role in reducing gully expansion and soil loss due to gully erosion in the Ethiopian highlands. Copyright © 2016 John Wiley & Sons, Ltd.

Hydrological Modeling in A Semi-Arid Region Using HEC-HMS

In this study, the Hydrologic Engineering Centre's Hydrologic Modeling System (HEC-HMS) model was employed to simulate runoff in the semi-arid region of northwestern China, specifically the Hailiutu watershed. The Hydrologic Engineering Centre's Geospatial Hydrologic Modeling Extension (HEC-GeoHMS) was used in conjunction with ArcHydro tools in an ArcMap geographical information system (GIS) environment to create input files of the catchment physical characteristics for the HMS model. The model was calibrated for the time period of 1978-1992. The results showed that the model systematically underestimated winter and spring hydrographs as well as a few summer flows. This was due to the discrepancy between the nonlinear rainfall-runoff response in the watershed and the linear structure of the Soil Moisture Accounting (SMA) model used. Also, the results pointed out that, due to data unavailability on hydraulic engineering in the Hailiutu watershed, the model faced challenges in simulating runoff properly and therefore could not be validated. Ultimately, the model's general performance in simulating runoff in the Hailiutu watershed was found unsatisfactory.

Assessing and Mitigating the Hydrological Impacts of Urbanisation in Semi-Urban Catchments Using the Storm Water Management Model

Urbanisation causes a range of adverse impacts on stream physical and ecological conditions due to increases in catchment runoff caused by increased imperviousness. Developing ways to reduce these impacts on in-stream ecosystems is a major challenge and requires innovative catchment specific, high-time-resolution modelling methods. We employed a combination of high-time-resolution data collection, analysis and modelling methods to understand the underlying hydrological processes and evaluate a potentially significant management option – stormwater harvesting. A set of sensitive parameters of the Storm Water Management Model (SWMM) were optimised using an automatic calibration method and hourly data in eight catchments in South East Queensland, Australia. Systematic investigation of the effects of urbanisation and its mitigation through stormwater harvesting was achieved by modelling the impacts of increasing impervious area for three of the relatively undeveloped catchments. As the extent of impervious areas across the catchments increased we typically found increases in the duration of high flow spells together with increases in mean flow and the frequency of runoff events. However, many hydrologic responses to increasing imperviousness were specific to the physical characteristics of catchments, and to the spatio-temporal pattern of urbanisation. By implementing stormwater harvesting options the hourly flows were reduced by up to 60 % but the maximum flow was unchanged. Thus the option was able to reduce, but not totally ameliorate, the negative hydrological impacts of increasing imperviousness.

Targeting flash flood potential areas using remotely sensed data and GIS techniques

Flash floods are the most common type of natural hazards that cause loss of life and massive damage to economic activities. During the last few decades, their impact increased due to rapid urbanization and settlement in downstream areas, which are desirable place for development. Wadi Asyuti, much like other wadis in the Eastern Desert of Egypt, is prone to flash flood problems. Analysis and interpretation of microwave remotely sensed data obtained from the Shuttle Radar Topography Mission (SRTM) and Tropical Rainfall Measuring Mission (TRMM) data using GIS techniques provided information on physical characteristics of catchments and rainfall zones. These data play a crucial role in mapping flash flood potentials and predicting hydrologic conditions in space and time. In order to delineate flash flood potentials in Wadi Asyuti basin, several morphometric parameters that tend to promote higher flood peak and runoff, including drainage characteristics, basin relief, texture, and geometry were computed, ranked, and combined using several approaches. The resulting flash flood potential maps, categorized the sub-basins into five classes, ranging from very low to very high flood potentials. In addition, integrating the spatially distributed drainage density, rainfall intensity, and slope gradient further highlighted areas of potential flooding within the Wadi Asyuti basin. Processing of recent Landsat-8 imagery acquired on March 15, 2014, validated the flood potential maps and offered an opportunity to measure the extent (200–900 m in width) of the flooding zone within the flash flood event on March 9, 2014, as well as revealed vulnerable areas of social and economic activities. These results demonstrated that excessive rainfall intensity in areas of higher topographic relief, steep slope, and drainage density are the major causes of flash floods. Furthermore, integration of remote sensing data and GIS techniques allowed mapping flood-prone areas in a fast and cost-effective to help decision makers in preventing flood hazards in the future.

Rainfall-runoff modelling using a spatially distributed electrical circuit analogue

The assessment and prevention of floods require appropriate forecasting and knowledge of the related hydrological processes. Due to the similar form of the governing equations, flood hydrograph shows a clear analytical and mathematical analogy with electrical circuits. In this paper, a spatially distributed hydrological model is developed which is analogue to a network of electrical resistance–capacitance with five circuits for describing the hydrological processes leading to floods. The spatially distributed hydrological model simulates rainfall, potential evapotranspiration, canopy interception, surface storage and soil storage. The parameters for analogical modelling were derived from translation of the physical catchment characteristics. A two-parameter Weibull equation aggregates the response functions of each pixel and calculates the hydrograph of the catchment. We applied the model to the ‘Open-Book’ or ‘tilted V-catchment’ theoretical benchmark problem, as well as to four hourly flood events and simulation of daily discharges. For the last two cases, data were used from the mountainous catchment of upper Tarqui in the Andes of Ecuador. Comparison of single versus multiple circuit designs for the benchmark problem indicates that the multiple circuit analogy provides a result similar to other hydrological models. The results further illustrate the usefulness of the methodology for flood modelling and how it can simplify the simulation for ungauged basins of temporal and spatial variations of influencing hydrological processes.

A Study on Development and Application of Island Type Water Balance Evaluation System

Korea repeatedly experiences floods and droughts that cause traumatic environmental conditions with huge economic impact. With an approach and solution such as Smart Water Grid these problems can be alleviated. Tapping into the retention ponds behind dams, rainfall harvest facilities in urban areas and any other structures installed to store rainfall water during flood events will mitigate the damage of flooding and provide a new source of national water resources. Similarly, purified waste water, ground water and desalinated sea water can also be feasible to use as alternative water resources. In this study, the water balance assessment model is being developed as a Smart Water Grid research. In fact, large proportions of water resources in Korea rely on a river fresh water. Also in the Youngjongdo island, tap water from water purification plant which use original source from the Han river. However the water supply system in the island is quite dangerous since the water purification plant is located in Incheon city and the water comes to island through the sea and no other source is used in the island. Therefore, once the accident at main water pipe in the sea, no water is available in this island. Information on water availability and water needs are crucial to identify hot spots of quantitative pressures on water resources. In this study, all available alternative water sources are calculated by the model developed through this study. Several physical and stochastic models on hydraulic and hydrological approaches are nominated to investigate physical characteristics of catchments

Performance assessment and improvement of recursive digital baseflow filters for catchments with different physical characteristics and hydrological inputs

Recursive digital filters (RDFs) are one of the most commonly used methods of baseflow separation. However, how accurately they estimate baseflow and how to select appropriate values of filter parameters is generally unknown. In this paper, the output of fully integrated surface water/groundwater (SW/GW) models is used to obtain optimal parameters for, and assess the accuracy of, three commonly used RDFs under a range of physical catchment characteristics and hydrological inputs. The results indicate that the Lyne and Hollick (LH) filter performs better than the Boughton and Eckhardt filters, over a larger range of conditions. In addition, the optimal values of the filter parameters vary considerably for all three filters, depending on catchment characteristics and hydrological inputs. The dataset of the 66 catchment characteristics and hydrological inputs, as well as the corresponding simulated total streamflow and baseflow hydrographs obtained using the SW/GW model, can be downloaded as Supplementary material.