Rainfall Loss Research Articles

Effect of rainfall and swath density on dry matter and composition change during drying of switchgrass and corn stover

During field drying, crops can be subjected to rainfall losses due to leaching, respiration and mechanical treatments. The objective of this study was to measure the impact of rainfall amount (8–75 mm) and crop density (0.8–2.6 (corn stover), 1 to 3.2 (switchgrass) kg [DM] m−2) on dry matter and composition change of corn stover (CS) and switchgrass. CS and switchgrass lost 0.3–4.7% and 0.2–2.8% as leaching loss from 8 to 75 mm of rainfall, respectively. After the incubation period of 48 h, the dry matter loss increased to 7.2–9.8% (CS) and 2.6–6.1% (switchgrass) from 8 to 75 mm of rainfall, respectively. Water soluble portion of CS and switchgrass was more severely affected than the fibre portion. Corn stover, being more exposed to rainfall in low density (LD) swaths, lost 56.7% ash content, compared to 19% in high density (HD) swaths. In CS, a significant decrease of K (10.2–63.8%) and Mg (5.6–41.7%) was observed with greater reductions in LD swaths compared to HD swaths. Similarly, a significant decrease in K (6.2–23.0%) and Mg (5.1–17%) content was observed in switchgrass but it was less prominent than CS.

The groundwater balance in alluvial plain aquifer at Dehgolan, Kurdistan, Iran

In this research, groundwater balance in Dehgolan plain, Kurdistan, Iran was carried out to assess changes in the level and volume of groundwater and water resources management. For this purpose, water resources supplies and consumption data, amount of charging and discharge and water level data recorded from wells and piezometers from 2010 to 2011 water year were gathered and analyzed. Rainfall and water losses of the study area were determined and required maps, including Iso-maps of the temperature, the evaporation, the groundwater level and the aquifer conductivity, were drawn by GIS software. Using the information and drawn maps and the equality of inputs and outputs data, the aquifer water balance was calculated. The results of balance equations showed that the balance is negative indicated a notably decline of groundwater equal to 15.029 million cubic meter (MCM). Such rate of decline is due to the large number of agricultural wells in the region, without considering the hydrological potential of the aquifer.

Modeling Rainfall Interception Loss for an Epiphyte-Laden Quercus virginiana Forest Using Reformulated Static- and Variable-Storage Gash Analytical Models

AbstractBarrier island forests are sensitive to changing precipitation characteristics as they typically rely on a precipitation-fed freshwater lens. Understanding and predicting significant rainfall losses is, therefore, critical to the prediction and management of hydrometeorological processes in the barrier island forest ecosystem. This study measures and models one such loss, canopy rainfall interception, for a barrier island forest common across subtropical and tropical coastlines: epiphyte-laden Quercus virginiana on St. Catherine’s Island (Georgia, United States). Reformulated Gash analytical models (RGAMs) relying on static- and variable-canopy-storage formulations were parameterized using common maximum water storage (minimum, mean, maximum, and laboratory submersion) and evaporation (Penman–Monteith, saturated rain–throughfall regression, and rain–interception regression) estimation methods. Cumulative interception loss was 37% of rainfall, and the epiphyte community contribution to interception loss was 11%. Variable-storage RGAMs using inferred evaporation and maximum water storage estimates performed best: mean absolute error of 1–2 mm, normalized mean percent error of 15%–25%, and model efficiency of 0.88–0.97, resulting in a 2%–5% overestimate of cumulative interception. Static- and variable-storage RGAMs using physically derived evaporation (Penman–Monteith) underestimated observed interception loss (40%–60%), yet the error was significantly lowered for submersion estimates of maximum water storage. Greater apparent error when using Penman–Monteith rates may result from unknown drying times, evaporation sources, and/or in situ epiphyte storage dynamics. As such, it is suggested that future research apply existing technologies to quantify evaporative processes during rainfall (e.g., eddy covariance) and to develop new methods to directly monitor in situ epiphyte water storage.

Influence of water management on the water cycle in a small watershed irrigation system based on a distributed hydrologic model

Based on the hydrological characteristics of a rice-based irrigation system in Southern China, the SWAT (Soil and Water Assessment Tool) model was modified in order to develop the Rice Irrigation System-Soil and Water Assessment Tool (RIS-SWAT). The irrigation water movement, water balance module, and rice yield calculations of the paddy field were improved within the SWAT model. In addition, the seepage of the irrigation canal and the pond’s effect on the irrigation modules were added to the RIS-SWAT. The impact of water management on the water cycle of the small watershed irrigation system (SWIS) was evaluated by conducting a scenario analysis with RIS-SWAT. The results indicated that an increase in the maximum water ponding depth of a paddy field could decrease irrigation water and rainfall loss. The canal water supply was reduced by 20%, resulting in an increase in irrigation water productivity without a reduction in the rice yield. The temporal and spatial distributions of the irrigation water in different subbasins did not significantly affect the water cycle within the SWIS. Furthermore, when the canal water supply was reduced by 20–40% and the pond water supply was increased, the rice yield was not affected. Thus, the water productivity of irrigation systems could be improved through the implementation of water management policies and practices that reduce field outflows and reuse the return flows captured by ponds.

Canopy Interception for a Tallgrass Prairie under Juniper Encroachment

Rainfall partitioning and redistribution by canopies are important ecohydrological processes underlying ecosystem dynamics. We quantified and contrasted spatial and temporal variations of rainfall redistribution for a juniper (Juniperus virginiana, redcedar) woodland and a tallgrass prairie in the south-central Great Plains, USA. Our results showed that redcedar trees had high canopy storage capacity (S) ranging from 2.14 mm for open stands to 3.44 mm for closed stands. The canopy funneling ratios (F) of redcedar trees varied substantially among stand type and tree size. The open stands and smaller trees usually had higher F values and were more efficient in partitioning rainfall into stemflow. Larger trees were more effective in partitioning rainfall into throughfall and no significant changes in the total interception ratios among canopy types and tree size were found. The S values were highly variable for tallgrass prairie, ranging from 0.27 mm at early growing season to 3.86 mm at senescence. As a result, the rainfall interception by tallgrass prairie was characterized by high temporal instability. On an annual basis, our results showed no significant difference in total rainfall loss to canopy interception between redcedar trees and tallgrass prairie. Increasing structural complexity associated with redcedar encroachment into tallgrass prairie changes the rainfall redistribution and partitioning pattern at both the temporal and spatial scales, but does not change the overall canopy interception ratios compared with unburned and ungrazed tallgrass prairie. Our findings support the idea of convergence in interception ratio for different canopy structures under the same precipitation regime. The temporal change in rainfall interception loss from redcedar encroachment is important to understand how juniper encroachment will interact with changing rainfall regime and potentially alter regional streamflow under climate change.

A catchment as a simple dynamical system: Characterization by the streamflow component approach

Summary The simple dynamical system approach was implemented to analyze, explain and simulate streamflow fluxes in diverse seasonal hydrological conditions within the forested Padež stream catchment in SW Slovenia. The catchment is characterized by the flushing, torrential hydrological response conditioned by the flysch geological settings of a low hydraulic conductivity. Consequently, the streamflow formation is not controlled solely by the deeper subsurface catchment storage but is also strongly influenced by the rainfall–runoff that bypasses the deeper subsurface part of the total catchment storage. Therefore, fast component of the streamflow is identified using two-component hydrograph separation; the component recession behavior is described by a separate sensitivity function and used in a simple model to simulate the streamflow. According to the simulation results, the Padež stream catchment behaves primarily like a deeper subsurface storage-dependent system during most of the hydrological conditions. When rainfall intensities increase (rainfall intensities close to 10 mm/h or higher), triggering of the secondary streamflow formation mechanism described by separate, bypassing flow sensitivity function becomes evident and causes fast hydrograph formation with steeply rising and falling limbs. To be able to implement the modeling concept for streamflow predictions, the rainfall losses, most likely associated with interception losses not covered under the potential evapotranspiration calculation, would have to be more thoroughly analyzed through rainfall interception measurements. Our study shows the possible way that two hydrological concepts, the streamflow recession analysis and the two-component hydrograph separation based on relatively easily measurable tracers, such as electrical conductivity, could be combined for analyzing streamflow fluxes.

Синоптические условия выпадения обильных осадков на территории Северного Казахстана в вегетационный период

В статье изучены условия выпадения обильных осадков в вегетационный период на территории Северного Казахстана. Изучение обильных атмосферных осадков представляет, как научный, так и практический интерес. Рассмотрена повторяемость осадков свыше 25 мм для пяти станций. Приведены наибольшие суточные количества осадков по месяцам, дан анализ синоптических условий и выявлены типы процессов, приводящие к интенсивным осадкам. Рассмотрены конкретные случаи выпадения значительных ливней. Қазақстанның солтүстік аймағында вегетациялық кезеңдегі қарқынды жауын-шашындардың түсуін зерттеу ғылыми және практикалық қызығушылық тудырады. Мақалада бес станция үшін 25 мм-ден артық түскен жауын-шашындардың қайталанушылығы қарастырылған. Айлар бойынша жауын-шашындардың ең үлкен тәуліктік мөлшері көрсетілген. Синоптикалық жағдайлардың талдауы берілген және қарқынды жауын-шашындарды туғызатын процестердің түрлері айқындалған. Қарқынды нөсерлердің түсуінің жеке жағдайлары қарастылған.

A combined rainfall infiltration model based on Green–Ampt and SCS‐curve number

AbstractThe Green–Ampt infiltration equation is an incomplete governing equation for rainfall infiltration due to the absence of an inertia term. The estimation of the capillary pressure head at the wetting front is difficult to determine. Thus, a major limitation of the Green–Ampt model is the constant, non‐zero surface ponding depth. This paper proposes an integrated rainfall infiltration model based on the Green–Ampt model and the SCS‐CN model. It achieves a complete governing equation for rainfall infiltration by momentum balance and the water budget based on the Green–Ampt assumption, and uses the curve number from the SCS‐CN method to calculate the initial abstraction, which is used as a basic parameter for the governing equation of the intensity of rainfall loss during the runoff period. The integrated rainfall infiltration model resolves the dilemma for capillary pressure head estimation, overcomes the limitation of constant, non‐zero surface ponding depth, and facilitates the calculation of runoff for individual flood simulations. Copyright © 2014 John Wiley & Sons, Ltd.

Erodibilidade de um Cambissolo Húmico sob chuva natural

A estimativa de perdas de solo é fundamental para o planejamento conservacionista. Com essa finalidade, destaca-se no Brasil o uso da Equação Universal de Perdas de Solo (USLE), para cuja utilização há escassez de dados obtidos de acordo com o método-padrão desse modelo. Entre os fatores que compõem a USLE, a erodibilidade do solo (fator K) é de difícil obtenção em razão da necessidade de conduzir experimentos em campo por longo tempo sob chuva natural. Com o objetivo de quantificar a erodibilidade do solo em um Cambissolo Húmico em Lages, SC, utilizando-se do método-padrão da USLE, quantificaram-se a erosividade (EI30) das chuvas naturais e as respectivas perdas de solo durante o período de 1993 a 2012. A erodibilidade foi determinada pelo quociente entre essas variáveis e pela regressão linear simples dessas. O valor de erodibilidade anual estimado pelo quociente e pela regressão linear simples entre as perdas de solo e as erosividades foi respectivamente de 0,0175 e 0,0172 Mg ha h ha-1 MJ-1 mm-1. A erodibilidade nos períodos de primavera-verão e outono-inverno apresentou pequenas variações em relação à média anual. A erodibilidade mensal variou de 0,0083 Mg ha h ha-1 MJ-1 mm-1 no mês de dezembro a 0,0241 Mg ha h ha-1 MJ-1 mm-1, no mês de abril. Ao longo do período de tempo avaliado, a erodibilidade anual evidenciou maior incremento nos anos iniciais e menor incremento nos anos finais.

Using scenario planning to evaluate the impacts of climate change on wildlife populations and communities in the Florida Everglades.

It is uncertain how climate change will impact hydrologic drivers of wildlife population dynamics in freshwater wetlands of the Florida Everglades, or how to accommodate this uncertainty in restoration decisions. Using projections of climate scenarios for the year 2060, we evaluated how several possible futures could affect wildlife populations (wading birds, fish, alligators, native apple snails, amphibians, threatened and invasive species) across the Everglades landscape and inform planning already underway. We used data collected from prior research and monitoring to parameterize our wildlife population models. Hydrologic data were simulated using a spatially explicit, regional-scale model. Our scenario evaluations show that expected changes in temperature, precipitation, and sea level could significantly alter important ecological functions. All of our wildlife indicators were negatively affected by scenarios with less rainfall and more evapotranspiration. Under such scenarios, habitat suitability was substantially reduced for iconic animals such as wading birds and alligators. Conversely, the increased rainfall scenario benefited aquatic prey productivity and apex predators. Cascading impacts on non-native species is speculative, but increasing temperatures could increase the time between cold events that currently limit expansion and abundance of non-native fishes, amphibians, and reptiles with natural ranges in the tropics. This scenario planning framework underscored the benefits of proceeding with Everglades restoration plans that capture and clean more freshwater with the potential to mitigate rainfall loss and postpone impacts of sea level rise.

Evaluating Starter N Application to Soybean With CROPGRO-Soybean Model in the Southern Guinea Savanna Agro-Ecology of Nigeria

Nitrogen (N) is essential for the growth and development of crops. It is a major soil nutrient for soybean. Deficiency of nitrogen in soil before soybean root nodule formation constitutes the most limiting factor after soil moisture for its production. This study was undertaken to determine starter N application rate for optimum soybean yield for two soybean varieties; assess Cropgro-soybean model and project soybean yield under different N use. Two field experiments were set up in a 5 × 2 split-plot arrangement in a randomized complete block design in 2009 and 2010. The N doses of 0 (control), 5, 15, 25 and 35 kg N/ha were applied one week after planting using urea to form the main plot and soybean varieties (TGx1485-1D and TGx1448-2E) constituted the sub-plot with three replications. Designated samples were used to evaluate 100 seed weight, plant dry biomass and harvest index. Data obtained were subjected to analysis of variance and means separated with least significant difference at p ? 0.05. Crop phenological data and yield at harvest were used for Decision Support System for Agrotechnology Transfer (DSSAT) Cropgro-Soybean model calibration and yield projection under different N use. Root mean square error (RMSE) and percentage error (PE) were used to analyze model outputs. The soil water balance output of the model was reviewed for explaining the components of water output in the environment. Field studies showed significant differences (p ? 0.05) in varietal response to seed weight and biomass production where variety TGx1448-2E produced a significantly higher 100 seed weight and higher plant dry biomass. Genotypic superiority of TGx1448-2E over TGx1485-1D is suggested. There was high accuracy in prediction of soybean phenology (i.e. PE < 10%) for both varieties, although high PE (> 15%) were obtained for yields of TGx1448-2E. The model accurately predicted soybean phenology to within 0-1 day of the field observed values. The soil water balance indicated 39-45 % loss of the total seasonal rainfall to runoff and 3-11 % through deep drainage. The application of N starter-dose was not effective in enhancing yield of soybean in the study-sites owing to the occurrences of intensive rainfall events that led to runoff and the loss of applied N during the cropping season.

Modified rational unit hydrograph method and applications

The modified rational method (MRM) is an extension of the rational method to develop triangular and trapezoidal runoff hydrographs. A trapezoidal unit hydrograph (UH) was developed from the MRM for the case when the duration of rainfall is less than the time of concentration of the watershed and is called the modified rational unit hydrograph (MRUH). The MRUH method was applied to 1400 rainfall-runoff events at 80 watersheds in Texas. Application of the MRUH method involved three steps: (a) determination of rainfall excess using the runoff coefficient; (b) determination of the MRUH using drainage area and time of concentration; and (c) simulating event runoff hydrographs. The MRUH performed as well as the Gamma function UH, Clark-HEC-1 UH and NRCS curvilinear UH methods when the same rainfall loss model was used. The MRUH method can be applied to time-variable rainfall distributions and at watersheds with drainage areas greater than typically used for the rational method (a few hundred acres).

Analysis of storage volume and reliability of the rainwater harvesting tanks in the coastal area of Bangladesh

The annual average rainfall in the coastal area of Bangladesh is more than 2,400 mm and rainwater harvesting (RWH) has been practiced for a long time for drinking water supply. For household RWH, the capacity of the storage tanks varies from 1,000 to 5,000 litres, which are the model-type storage tanks provided under several RWH programs of government and NGOs. The optimum storage tank volume has not been investigated considering family size and demand, roof types and rainfall. As a result, most of the households can avail water from rainwater tanks for about six months and rest of the year, they have to depend on other unreliable and distance sources. With the aim of developing a comprehensive decision support tool for a reliable RWH system, design curves for the storage volume were developed for three climatic conditions (i.e. dry, average, and wet years), available roof catchment area (10–50 m2), rainfall loss factor and household demand (2–12 lpcd) for a typical six members family using mass curve. Moreover, a spreadsheet-based daily water balance model was developed to assess the reliability of the currently used water tanks (1,000–5,000 L). The analysis showed that the currently used tanks are insufficient to meet the year-long drinking and cooking water demand. Under average and dry climatic conditions, the achievable reliability does not significantly varies with increase of catchment area and tank size; and the maximum achievable reliability is about 70%. A large quantity of water is lost as spilled water even with a tank size of 5,000 L. This water can be used for other purposes if larger tanks are used to capture the excessive spilled water.

Changes of rural to urban areas in hydrograph characteristics on watershed divisions

This study examined changes in hydrograph characteristics of rural statuses to urban statuses on watershed divisions in Taiwan. The main approach was to relate applicable model parameters with the corresponding imperviousness based on calibration and verification using a semidistributed model and 102 events. The model structure is conceptual linear reservoirs with parallel-type cascaded storages which is represented by overland and channel coefficients. The hourly mean rainfall of the watershed and its divisions were calculated using the Kriging method. The time-variant rainfall losses were calculated using the constant percentage method. The spatial and temporal model inputs, division effective rainfall, were obtained by subtracting mean rainfall of divisions from the rainfall losses. In calibration, the storage values of 50 events derived using appropriate parameter bounds were more reasonable than those using inappropriate bounds. Based on the optimal interval method, the overland storages displayed more marked change than did channel storage in response to imperviousness changes. By contrast, the channel storages were unaffected by the changes in urbanization. The overland storages were related with the imperviousness by using the regression equations for determining their relationships in continuous changes of urbanized divisions. The verification of the regression relationships was based on 52 events. The results indicated that power linkage was an available selection for linking division parameters with the corresponding imperviousness. Finally, the study concludes (1) appropriate bounds in parameter calibration are useful for obtaining significant storage values and (2) the study results using these suitable storages indicated large changes in imperviousness on the downstream divisions, marked urbanization resulted in reduced the time to peak at least 10 %, the peak discharge exceeded an increment of 20–30 %.

Measuring and modeling rainfall interception losses by a native Banksia woodland and an exotic pine plantation in subtropical coastal Australia

Rainfall loss by canopy interception and subsequent evaporation to the atmosphere can be a significant portion of water loss from forested ecosystems. To quantify and compare interception losses from two forest types (exotic pine plantation vs. displaced native Banksia woodland) on Bribie Island in subtropical east coast Australia, we measured gross rainfall, throughfall and stemflow over a one-year period (May 2012–April 2013). Interception losses from both forests were also simulated by the revised Gash’s analytical model (RGAM) and the WiMo model. The results show that the annual interception loss in the Banksia woodland was lower (16.4% of gross rainfall) than that in the pine plantation (22.9% of gross rainfall) over the study period, which can be explained by the lower canopy storage capacity and higher aerodynamic resistance of the Banksia woodland. Using fixed parameters obtained from wet season (November–April), the optimized RGAM and WiMo models predict the interception losses from both forest stands reasonably well, with an underestimation of 8.5–12.7% for the dry season (May–October), and a total underestimation of 5.2–8.2% for the entire year. The results indicate the development of commercial pine plantations in these areas would result in an increase in interception losses and thus reduce the net rainfall input in these forested ecosystems.

On climate variability and civil war in Asia

Effects of climate change are frequently claimed to be responsible for widespread civil violence. Yet, scientists remain divided on this issue, and recent studies suggest that conflict risk increases with higher rainfall, loss of rainfall, higher temperatures or none of the above. Lack of scientific consensus is driven by differences in data, methods, and samples, but may also reflect a fragile and inconsistent correlation for the habitual spatiotemporal domain, Sub-Saharan Africa post-1980. This study presents a comprehensive, multi-scale empirical evaluation of climate-conflict connections across Asia, the continent with the highest conflict rate per country. We find little evidence that interannual climate variability and anomalies are linked to historical conflict risk in the simple and general manner proposed by some earlier research. Although a significant parameter coefficient can be obtained under certain specifications, the direction and magnitude of the climate effects are inconsistent and sensitive to research design. Instead, Asian civil wars share central features with violent events elsewhere, proving the main correlates of contemporary armed conflict to be economic and socio-political rather than climatological.

Application of a continuous Rainfall-Runoff model to the basin of Kosynthos river using the hydrological software HEC-HMS

&lt;div&gt; &lt;h1 style="text-align: justify;"&gt;&lt;span style="font-size:11px;"&gt;&lt;span style="font-family:arial,helvetica,sans-serif;"&gt;In this paper, the application of a continuous rainfall-runoff model to the basin of Kosynthos River (district of Xanthi, Thrace, northeastern Greece), as well as the comparison of the computational runoff results with field discharge measurements are presented. The rainfall losses are estimated by the widely known Soil Conservation Service-Curve Number model, while the transformation of rainfall excess into direct runoff hydrograph is made by using the dimensionless unit hydrograph of Soil Conservation Service. The baseflow is computed by applying an exponential recession model. The routing of the total runoff hydrograph from the outlet of a sub-basin to the outlet of the whole basin is achieved by the Muskingum-Cunge model. The application of this complex hydrologic model was elaborated with the HEC-HMS 3.5 Hydrologic Modeling System of the U.S. Army Corps of Engineers. The results of the comparison between computed and measured discharge values are very satisfactory.&lt;/span&gt;&lt;/span&gt;&lt;/h1&gt; &lt;/div&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

영국의 설계홍수량 산정모형인 FEH-ReFH의 국내 남천유역 적용성 평가

ABSTRACT The purpose of this study is to evaluate the applicability of UK design flood estimation model, FEH-ReFH through rainfall-runoff simulation of Korean watershed. For the Nam stream watershed(165.12㎢), the model was calibrated using 6 storm events. The watershed and hydrological characteristics for the model requirements was prepared by developing input data pre-processors based on open GIS. The parameters of rainfall loss rate and unit hydrograph were calibrated from the observed data. The results can be used for improving and standardizing the Korean design flood estimation method. 2013년 6월 6일 접수 Received on June 6, 2013 / 2013년 8월 19일 수정 Revised on August 19, 2013 / 2013년 9월 3일 심사완료 Accepted on September 3, 2013* 본 연구는 국토교통부 물관리연구사업의 연구비지원(11기술혁신C06)에 의해 수행되었음.1 건국대학교 사회환경시스템공학과 Dept. of Civil & Environmental Systems Engineering, Konkuk University2 한국건설기술연구원 수자원연구실 Water Resources Research Division, Korea Institute of Construction Technology※ Corresponding Author E-Mail : kimsj@konkuk.ac.kr

A Method for Estimating the Regional Initial and Constant Loss for Design Flood Estimation in West Peninsular Malaysia

Floods are known as one of the world’s most frequent and devastating events. Techniques to predict and estimate the size of floods is depend on the availability of hydrological data. Using the conceptual of lump model, rainfall-runoff method is widely used in design flood estimation, which represents the input of rainfall and catchment characteristics such as rainfall depth, rainfall intensity, baseflow and losses. 7o calculate the catchments runoff, amount of losses shall be determine accurately by considering various source of the rainfall losses such as evaporation, inßltration, interception, depression storage and loss in groundwater recharge. In Malaysia, the common technique to estimate the hydrological losses is using initial and constant loss method. Furthermore, the value has been used in Urban Stormwater Manual for Malaysia (USMA) are adopted from the other literatures which is not represented the value from local catchment.7he objective of this study is to derive the initial and constant loss values using the data from selected local catchments in west Peninsular Malaysia. 7he calculated initial and constant loss will be further used to derive design flood discharge based on the design rainfall. An initial loss and constant loss model was examined in this study to observe the loss rate parameters in heterogeneous catchments and evaluate their signißcance as well as their potential influence on design peak floods. 7he study has been utilised the rainfall and runoff data from 113 storms over 15 catchments. 7he loss parameters were obtained from model optimi3ation using the HEC-HMS Modeling program. From the analyses, the median initial loss is 21.54mm with the standard deviation 7.85mm. 7he value shows higher than the value adopted in USMA. Meanwhile, the value for constant loss is 8.07mm which between the range of USMA. Based on the ßndings of design initial loss analyses, the values of initial loss were 49.3, 57.6, 64.1, 69.4, 73.3 and 76.6 for ARI 2,5,10,20,50 and 100, respectively. 7he percentage error between design initial loss and constant loss method and flood frequency method shows good results which are most of the percentage error less than 35%. It shows that the design initial loss and constant loss method produce reasonable accurate results when compared to the rainfall-runoff method and flood frequency method. Based on the ßndings, it can be suggested that the regional design initial loss and the constant loss rates would be able to serve reasonably well in determining catchment loss for the design purposes.

토양수분과정을 고려한 GR4J 모형의 개량 및 국내유역 적용성 평가

토양수분과정은 강우사상 발생 시 유역의 반응을 결정할 때 중요하게 고려되어야 할 과정으로 저류형 수문모형에 있어서 초기 유출량을 결정하는 역할을 한다. 이 같은 토양수분과정은 연속형 NRCS 방법에 주로 사용되었으나 초기강우손실 가정의 문제점 때문에 강우발생사상에 대하여 일부 사상은 설명할 수 없다. 본 연구에서는 NRCS 방법의 초기강우손실 가정의 문제점을 해결하고자 수정된 토양수분과정을 고려하여 모형을 개량하고 개량한 모형을 국내유역에 적용하여 적용성을 평가하였다. 수정된 토양수분과정 개선절차 적용에 있어서 집중형 장기강우유출모형인 GR4J(Ge'nie Rural a 4 parame tres Journalier)를 선택하여 개선하였다. 이를 기존의 결과와 비교하여 개선된 절차가 결과에 어떤 영향을 미치는 지 살펴보았다. 이 과정에서 모형의 매개변수 추정은 최적화 알고리즘인 화음탐색법을 사용하였으며 매개변수 검증을 수행하여 각 매개변수가 유역의 특성을 대표하는지 확인하였다. 토양수분과정 개선을 통해 더 향상된 강우-유출 값을 획득하였으며 연구 결과를 토대로 토양수분과정 개선을 통해 강우-유출 과정의 정확성을 향상시킬 수 있음을 확인하였다. 유출기준저류고에 따른 토양수분과정 세분화는 유출량 추정의 정확성을 높이는 데 매우 중요한 역할을 하며 본 연구에서 사용한 GR4J 모형은 비교적 적은 매개변수를 사용하여 우수한 성능을 나타내기에 본 연구결과를 바탕으로 국내유역에서 적용하기에 적합한 모형으로 기대된다. Soil Moisture Accounting(SMA) process is an important topic in rainfall-runoff analysis because it determines the initial discharge in hydrological models. The SMA process is used in continuous NRCS method. However, it can not explain some events due to its assumption of initial rainfall losses. In this study, a modified SMA procedure is applied to solve the problem with the initial rainfall losses assumption of the NRCS method, and a modified GR4J model is developed using the modified SMA procedure. To verify the applicability of the proposed model, the results are compared with those from existing GR4J models in three different Korean basins. In this process, Harmony Search optimization algorithm is used to calibrate model parameters. And the calibrated parameters are verified to check the representability of the target basin. The developed model shows better results than existing models do and can improve accuracy of the rainfall-runoff model. Since the modified GR4J model shows outstanding efficiency while using less parameters, it is expected to be applied to many other Korean basins.