Temporal Adjustment of Channel Geometry and Spatial Changes in Riverbed Materials along the Downstream Channels of Large Dams in the Geum River basin

In order to establish fundamental data for stream restoration and environmental flow, we investigated inhabitation and species diversity of fish to substrate size in the typical streams of Geum River Basin. Field monitoring including fish sampling was conducted from October 2007 to October 2009. Substrate size was determined according to six different : silt (Si), sand (Sa), fine gravel (Fg), coarse gravel (Cg), cobbles (Co) and boulders (Bo). A total number of fish caught in the 18 sites was 7,649 representing 10 families 50 species, and Si, Sa, Fg, Cg, Co and Bo stations occupied 30, 29, 38, 30, 27 and 17 species, respectively. The most frequently found species in number was pale chum (Zacco platypus, 29.7%, n=2,275) followed by Z. koreanus (22.5%, n=1,720) in total stations. Biological diversity with increase of substrate size from the dominance of part species showed higher values as dominance index, lower and diversity, richness and evenness index. Index of biological integrity (IBI) and qualitative habitat evaluation index (QHEI) scores decreased with increase of substrate size. Therefore, it is necessary to make an effort on stream rehabilitation with evaluation of physical habitat condition by indicator species in order to maintain biodiversity and perform ecological restoration.

Evaluation of Land Use Change Impact on Hydrology and Water Quality Health in Geum River Basin

Analysis of extreme cases of climate change impact on watershed hydrology and flow duration in Geum river basin using SWAT and STARDEX

The objective of this study is to develop a standardized model for analyzing water balances in large scaled water basin by considering agricultural water districts, and to evaluate the hydrological feasibility of applying this model to several water districts such as Nonbul, Geumbok, Daejeon 1, Daejeon 2, and Cheonggang in Geum river basin. Ten types of stream network were considered in developed model. Using this model, streamflows were simulated by major stations and water balances were analyzed by water districts. Simulated streamflows and measured streamflows were compared at check stations such as Gapcheon and Bugang stations in which Nash and Schcliffe's model efficiencies were 0.633, 0.902, respectively. This results showed its applicabilities to national water resources plan, rural water development plan, and total maximum daily load plan in Korea.

The Geum River basin, located in the west-central part of the Korean Peninsula, is the third largest and minimally human-disturbed river basin in South Korea. Streamflow and available water resources from this basin is critical for water supply for agriculture. Due to the increased population, industrialization, and climate change, changes in streamflow and available water resources for the Geum River are expected. However, there are limitations in analyzing water resource changes in the Geum River Basin with discontinuous and relatively short observational streamflow records.In this study, we propose to dynamically downscale daily surface and base runoff data from the 10-km ERA5 reanalysis product via VIC-River Routing model. The VIC-River Routing model was ran at the 90-meter spatial resolution with geographical information to reconstruct long-term naturalized streamflow data over 1950-2021. In the VIC-River Routing model, the flow direction, stream order, and slope estimated from the 90-meter digital elevation model (DEM) over Geum River basin as the topographical parameters. This downscaled natural streamflow data will provide an opportunity to investigate hydroclimatic changes of the hydrologic regime of Geum River.

سیلاب ‌به‌عنوان یک فرایند ژئومورفیک رودخانه‌ای بر مورفولوژی درختان حواشی و بستر رود اثر می‌گذارد و منجر به پاسخ‌های رشدی متفاوتی در سری‌ حلقه‌های درخت می‌شود. درختان کج‌شده و زخم‌خورده یکی از رایج‌ترین انواع شواهد دندروژئومورفولوژیکی رخدادهای سیلابی گذشته در حواشی رودخانه‌ها‌ هستند و برای تاریخ‌گذاری و بازسازی رخدادهای ژئومورفیک گذشته مورد استفاده قرار می گیرند. زخم‌های ایجاد شده بر تنه درختان می‌تواند به‌عنوان شاخص های پالئواستیج برای بازسازی سطح و حجم سیلاب های قدیمی بکار رود. هدف این تحقیق بازسازی فراوانی رخدادهای سیلابی و سطح آن‌ها در رودخانه نکا با استفاده از آنالیز حلقه‌های رشد در درختان زخم‌خورده و پاسخ به این فرضیه است که " سطح سیلاب برآوردی از داده‌های دندروژئومورفولوژی در حوضه آبریز نکا بیشتر از داده‌های ایستگاهی است"؛ بنابراین پس از بازدید منطقه و جمع‌آوری داده های اولیه و تعیین موقعیت نمونه‌ها، تعداد 18 نمونه از تنه درختان زخم‌خورده در حاشیه و کناره‌های بستر نکارود برداشت شد. پس از آماده‌سازی نمونه‌ها تعداد و عرض حلقه‌ها با استفاده از میز دیجیتالی LINTAB و برنامه نرم‌افزاری TSAPWIN با دقت 01/0 میلی‌متر شمارش و اندازه‌گیری شد و سال وقوع سیلابها از طریق کاهش ناگهانی در روند افزایشی پهنای حلقه درخت بازسازی گردید؛ اما به‌منظور برآورد سطح سیلاب و تخمین دبی پالئوسیلاب‌ها بالاترین نقاط از بالاترین زخم ها به‌عنوان تخمینی برای دبی اوج در نظر گرفته شد و چهار مقطع عرضی از بستر اصلی رودخانه نقشه‌برداری شد تا ارتفاع سیل بر مبنای زخم‌های تنه درختان برآورد گردد. نتایج نشان داد که بیشترین تعداد زخم‌ها به ترتیب از سیلاب سال‌های 1387 با دبی پیک m3/sec130 و 1378 با دبی پیک m3/sec2000 منشأ گرفته‌اند. علاوه بر این سیل سال 1999 و نیز سیل سال 2003 با دبی پیک m3/sec361 بیشترین تأثیر را در روند رشد درختان حاشیه بستر داشته‌اند. همچنین دو سیلاب دیگر در سال 1320 و 1336 و مربوط به قبل از تأسیس ایستگاه هیدرومتری در منطقه بازسازی شد. این سیلاب‌ها زخم بزرگی را با ارتفاع حد بالایی زخم به طول cm270‌ از سطح زمین، بر روی ساقه درخت بر جای نهاده‌ و سطح سیلاب از طریق این زخم‌ به مقدار 37/4277 مترمکعب در ثانیه برآورد گردید که بزرگ‌ترین دبی سیلابی رودخانه نکا در طی صد سال‌ اخیر است و نشان می‌دهد که دبی‌های سیلابی و پیک رودخانه نکا که از طریق دندروژئومورفولوژی بازسازی شده‌اند بسیار بیشتر از دبی‌های ایستگاهی این رودخانه است.

This study attempted to analyze flow duration in a basin using a method to estimate environmental flow developed by the International Water Management Institute, and simulate the effects of runoff characteristics unique to a river and flow variability due to basin developments on aquatic ecosystems. To do so, KModSim, a simulation model for basin-wide water distribution, was used to assess flow duration in the Geum River basin, one of the four major river basins in Korea, by environmental management class (EMC). Flow duration curves by EMC at Sutong and Gongju sites were derived on the basis of natural flow in the Geum River basin. As a result, they were found to be consistent with the results of previous studies. Time series of mean monthly flow data by EMC were plotted together with those of simulated flow data by reservoir operation scenario; Sutong and Gongju points both showed flow behaviors corresponding almost to “A” in EMC. In addition, the characteristics of habitats by species of fish were identified through monitoring fish habitat at the Sutong site, so that optimal ecological flow rate was estimated. For this purpose, relations between flow discharge and weighted usable area for Coreoleuciscus splendidus and Pseudopungtungia nigra were projected using physical habitat simulation system, and EMCs consistent with flow duration curves (estimated taking in-stream flow) were assessed. The results or findings reported in this study are expected to serve as basic data for making a plan to efficiently monitor and manage aquatic ecosystems in the Geum River basin.

Dams on rivers alter the sediment continuum, trapping water and sediment in the upstream reservoirs. River reaches downstream are affected by several negative effects, such as bed incision, reduction of the river morphological variability, development of an armoured layer and depletion of ecological habitat for fish. The replenishment of sediment technique has been used since the 1970s to mitigate the lack of sediment transport in the downstream reaches of dams. The method is mainly used to re-establish a sediment continuum, restore a natural bed morphology and to recover spawning grounds for fish. Even if both experimental and field tests have been performed in the past, there is still a lack of knowledge regarding the necessary flow released from the bottom outlet of the dam, the amount of sediment and the configuration of the replenished deposits. This research aims at filling these gaps by means of experimental tests at the Laboratory of Hydraulic Constructions at Ecole Polytechnique Federale de Lausanne (EPFL). The main characteristics of an alpine stream were reproduced in a channel facility in terms of grain size distribution, slope and hydraulic conditions. The sediment replenishment technique was investigated as an influence to the geometrical configurations and volume of deposits, as well as applied discharge. The experiments showed that the bed morphological pattern created by the eroded replenishment material was linked to the initial geometrical arrangement of the replenishment volumes. When applying parallel configurations of replenishment volumes, a general bed fining was obtained with material spread over the entire channel width. Alternating replenishment positioning lead, in turn, to the creation of bed morphological patterns. The wavelength of these bed forms was seen to be related to the replenishment length. Both constant discharge and transient flow were investigated. Three submergence conditions of the replenishment were tested: unsubmerged, completely submerged and over-submerged. A complete submergence was optimal to obtain a complete erosion of the volumes with transport of the material along the channel and persistence of the material on the channel bed. Four slopes for the increasing and decreasing limb of triangular-shaped hydrographs, having the same maximum discharge, were tested and the results compared with the constant discharge cases. A discharge having a triangular distribution in time is similar to the operational condition of dams when releasing an artificial flood. Transient flows with steep rising limbs lead to a reduction of 70% of water consumption compared to a constant flow, although achieving the erosion of the replenished material. The application of the complete hydrographs showed to be counter-productive in terms of local effect of the sediment replenishment. These hydrographs may be useful for reaching longer distance impacts in sediment replenishment. Lastly, the effect of consecutive replenishment of sediments was investigated. A second replenishment can increase the deposition heights and volumes downstream. As expected, a second replenishment affects a longer downstream channel reach. Thus, consecutive replenishments are useful in field applications to have effects at longer downstream distances.

This dissertation argues that the floods following extreme precipitation result not only from very heavy rainfall but also from the significant impact of human activities on natural water systems. While most literature emphasises that the increasing magnitude of storm rainfall extends beyond the original protection standards of hydrologic facilities in highly populated delta cities. Based on the knowledge of urban morphology, this study analyses how human systems have affected the transformation of natural water processes in the Kaoping River Delta. The relationship between human environments and natural landscape is illustrated via a 3-layer analytical framework which consists of a natural landscape layer, an infrastructure layer and an occupation layer. This layer-based approach views landscapes as a whole system in which each element interacts with the others. In order to transcend the limitations of traditional urban morphology and the overlay-mapping method, this research initiates an analysis framework with the delta scale from a deductive perspective. Furthermore, it argues that the significant progress of infrastructure technology is the crucial factor to dominate the transformation of modern urban pattern. This influence could be identified by the analytic process of the 3-layer approach from the perspective of the delta or regional scale. This new starting point of a theoretical framework for analysing urban forms has been proved in the Kaoping Delta case. Furthermore, it could be a new and valid theoretical background to extend the knowledge of urban morphology. The formal transformation of the Kaoping Delta is divided into four main periods, which reveals human activities have affected the operation of natural systems since a century ago. From a delta scale perspective, those effects interacting between different layers can be identified in six different topographies (in italics) of the whole river catchment area. A. The dike system along the main stream in the plains protects delta cities against floods, which enables rapid urbanisation. Population growth in delta cities increases food demand, which causes the intensive agricultural cultivation of mountain areas. B. The dike system narrows the original riverbed in the river basin, which raises the water level of the river during storms. This situation blocks the drainage outlets of delta cities and induces higher frequencies of urban inundations. C. The dike system along the main stream in the plains has significantly changed the surface flowing path of river and dramatically decreased the recharge of groundwater in foothills. It causes serious land subsidence in coastal areas when the ground cannot obtain sufficient groundwater. D. The dike system and the bridges of transportation crossing river has resulted in the lag-sedimentation of the river in the river basin. When a significant amount of river sand deposits in the riverbed rather than being transited to the estuary to supply the demand for sand along the coast, it induces serious erosion in the coast. Following this context, this study organised a five day workshop in Kaohsiung, ‘Workshop on Water Environment Development in Kaohsiung’ in 2012 to further examine the results derived from Chapters 3 and 4, and to demonstrate how a 3-layer approach can work between multiple disciplines as a platform for collaboration. This workshop followed the theoretical framework of the 3-layers to explore the entire Kaoping River catchment area and its two tributary basins as the chosen local-scale sites: the Meinong River and the Love River. This workshop gives the best demonstration of how to practically utilise the 3-layer approach to organise multiple- disciplinary work, and then to make an integrated plan. The results and process of this workshop are also generalised as a framework, which could be applied to other cases.

This paper collates information on the current status of investigations and related handaxes in the Baise Basin over the last 50 years, focusing on the Fengshudao site, through a metrological analysis of handaxes Type,Shape, size, lithology and other attributes) and other areas (other sites in the Baise Basin, the Luonan Basin, the Imjin/Hantan River Basins , the Geum River Basin, the Yeongsan River Basin, the Acheulian handaxes in the western Old World) for comparative analysis and to understand their nature.
 The Baise handaxe belongs to the pebble industry in southern China. Because its cultural attributes include Acheulean technology, it occupies a pivotal position in the pebble culture of southern China and Asia. From its discovery in the early 1970s to the present, in the past 50 years, relevant investigations and research have achieved scientific research results, which have attracted widespread attention from the international academic community. Therefore, Chinese academic circles have also begun to discuss the ‘Movius line’. At present, there are 41 sites containing handaxes in the Baise Basin, and a total of 499 handaxes have been found. Among them, 11 were excavated from strata, and the rest were collected from the surface.
 The Fengshudao handaxes were basically made from large flakes and pebbles, with three types of stone: sandstone, quartzite and igneous rock. The sandstone is the most abundant and has the most stable ‘broadness’(B/L) and ‘flatness’(Th/B). According to the results of the metrological analysis, the ‘broadness’ (B/L) and ‘flatness’ (Th/B) indices of the Fengshudao handaxes are relatively high, and the ‘Pointness’ (B1/B2) index is relatively low. A comparison with other sites in the Baise Basin, the Luonan Basin, the Imjin/Hantan River Basins , the Geum River Basin, the Yeongsan River Basin, the Acheulian handaxes in the western Old World Acheulean handaxe shows that the Fengshudao handaxe is broader, thicker and has a more pointed base. In terms of industrial assemblages, handaxes and picks are common forms of assemblage in the Baise Basin, while Cleavers are rare, which is a clear difference from the Acheulian industry of the western Old World.

When establishing long- and short-term reservoir operation to support integrated water resources management, reservoir operation emphasizes not only water quantity but also water quality downstream of the reservoir. This study proposes a water quality projection scheme in the Geum River basin based on the pollutant loadings of biochemical oxygen demand, total nitrogen (TN), and total phosphorus (TP) combining with a long-term hydrologic simulation model. In the Geum River basin in Korea, two multipurpose dams, Daechung and Yongdam reservoirs, exist. Downstream of the Daechung reservoir is especially subject to the pollutant loadings released from the metropolitan cities which contribute to water quality degradation in the main stream of the Geum River. To identify the hydrologic cycle in the Geum River basin, long-term hydrologic simulation models have been employed and calibrated with two control points from 1983 to 2008. Water quality simulation based on the flow rates and pollutant loadings estimated in the Geum River basin shows a good agreement with observed ones along the main stream of the Geum River. As a result, the combination of water quality and the hydrologic simulation model provides systematic approach to project water quality downstream of the reservoir and to support reservoir operation in determination of discharge release considering downstream water quality.

These days, relics that used to have regional specificity tend to deviate from their specificity due to the active cultural property excavation research. It is necessary to recognize the newly identified area. Therefore, among the archaeological materials that strongly reflect regional specificity, we paid attention to the Miniature farming tools accumulated around the Geum River basin. The Miniature farming tools can be divided into ttabi type, cheolseo type, iron axe type, and sickle type. Data from the Geum River basin also show high excavation rates for Iron Axe type and sickle type, although the warm and cheolseo type are also identified. Cheoljun is one of the characteristic iron artifacts excavated from the Geum River basin. Compared to the Daegaya sphere, this was identified as a ttabi-type Miniature farming tool, and the plane shape and cross-sectional shape were considered to be more likely to have been produced under the influence of the Daegaya sphere rather than generated and produced within the Geum River basin. Iron axe-type Miniature farming tools are again divided into I-shaped and V-shaped in crosssectional form, and the I-shaped is the same as or similar to those confirmed in the Daegaya sphere, so it is thought to be highly relevant. On the other hand, the V-shaped is also excavated from the remains of the Proto-Three Kingdoms Period, which is confirmed around the Geum River basin, and is similar to the form of Iron axe, which has been produced and used for a long time, so it is thought that the traditional method was inherited. Although there is a limit to linking data excavated from the Geum River basin with Miniature farming tools excavated from the Daegaya sphere, data that are likely to have been produced in a manner similar to that of the Daegaya sphere in both plane and cross-sectional shapes were identified. From these data, it can be seen that there are also data that are more likely to have flowed into Baekje sphere from Daegaya sphere than from Baekje sphere.

The present study conducted a preliminary investigation of perfluorinated compounds (PFCs) within the Geum River Basin, focusing on potential contamination sources such as downstream areas, wastewater treatment plants, and major rivers in the basin. The targeted substances for this study were PFHxS (Perfluorohexane Sulfonate), PFOA (Perfluorooctanoic Acid), and PFOS (Perfluorooctane Sulfonate)—three PFCs that have been subjects of extensive research due to their environmental persistence and potential hazards. These substances are listed under the Stockholm Convention and are managed as water pollutants in South Korea. The findings of this study are intended to serve as foundational data for the management of PFCs in the region. A total of 15 sampling points were selected, focusing on key sites expected to influence the concentration of PFCs in the Geum River Basin, including 12 points from major downstream areas and wastewater treatment plants, as well as two tributaries (located in the middle and lower reaches of the Geum River) and one point along the main river. The three PFCs were analyzed using LC-MS/MS. Sample preparation was carried out following the water quality pollution testing standards (ES 04506.1) and the residual pollutants testing standards (ES 10390.1, ES 10363.1a). Solid-phase extraction (SPE) was performed using HLB cartridges to extract the compounds. The investigated downstream areas and wastewater treatment plants exhibited relatively high PFCs detection rates of over 94%. In some measurement points, PFOS and PFOA tended to show higher concentrations in the effluent compared to the influent. Additionally, while the concentrations in the rivers were low, below 10 ng/L, the presence of PFCs was confirmed across the entire Geum River Basin. At sites where effluent from wastewater treatment plants joined the river system, the total concentration of the three PFCs and the average concentration of PFOA were found to be the highest, indicating that wastewater treatment plants could be significant sources of PFC contamination. The concentrations of PFCs detected in the treatment plant processes were highest in the effluent from the primary sedimentation tank, followed by the effluent from the secondary sedimentation tank, influent to the secondary sedimentation tank, and influent to the primary sedimentation tank. For most substances, except for PFHxS, the concentrations in the effluent were either higher or similar to those in the influent, suggesting that PFCs were not efficiently reduced in the treatment plants, with some showing an increasing trend. This study confirmed the widespread presence of PFCs throughout the Geum River Basin. It is necessary to identify and address the major sources of these contaminants while conducting continuous monitoring to study their behavior in the environment. Furthermore, to better understand the impacts of these persistent pollutants, additional research is needed, including the analysis of various other PFCs and their precursors, beyond the commonly studied PFOS, PFOA, and PFHxS.

The analysis of variability of riverbed elevation recorded at five selected gauging cross-sections of Nida River, and at three gauging stations of Czarna Nida is presented in the paper. The studies concern the period of 60 – 80 years of observation. The trends of riverbed changes during the study period at the selected gauging stations were calculated based on the variability of observed minimal annual water stages. The reasons for the observed changes in the river course and channel geometry are given. These changes were caused by river regulation consisted of the shortening and narrowing of the river channel. Moreover, grain size distribution analysis in the selected gauging stations of Nida River and characteristic diameter variability of sediments along the river course examination are presented. These analyses were to evaluate the variability of characteristic diameters along the river course in connection with observed changes in cross-sections’ geometry. Additionally, to confirm the process of erosion or deposition recognized in the examined river channels, hydrodynamic equilibrium was determined. Three methods were proposed and used: the mean velocity and critical velocity in the main river channel comparison, the stream power value calculation which defines the character of the river channel, and the WWK (index of cutting or shallowing of the river channel) index.

از ویژگی‌های بارز رودخانه کرخه در غرب استان خوزستان به ویژه در دشت آزادگان، دینامیک فعال آن است. بررسی این پویایی و تعیین نقش آن در ایجاد مخاطرات محیطی و ساختار فضایی منطقه، مستلزم شناخت مورفودینامیک رودخانه از گذشته تا حال بر اساس شواهد رسوبی و هیدرومورفولوژی است؛ زیرا مورفودینامیک رودخانه ها به خصوص در دشت های سیلابی معلول شرایط رسوب گذاری و وقایع محیط شناسی مانند تغییرات آب و هوایی و تغییرات سطح اساس آب هاست. بدین منظور، پس از جمع‌آوری داده‌ها، تغییرات مسیر رودخانه و شرایط محیط های رسوبی به عنوان متغیر مستقل و عناصر فضایی مانند تغییر در اندازه ذرات رسوبی، تپه‌های ماسه‌ای، کاربری های کشاورزی، مسکونی و غیره به عنوان متغیرهای وابسته در نظر گرفته شدند. ابتدا با استفاده از روش‌های پردازش رقومی بر روی تصاویرماهواره ای لندست سال‌های 1990،1993،1998،2002 میلادی و سنجنده Liss از ماهواره IRS هند سال 2006 میلادی و ثبت نقاط شاخص در بازدیدهای میدانی، مسیرهای متروکه بازسازی و مسیرهای فعال بررسی شدند. در ادامه با تطبیق مسیرهای رودخانه با سایر لایه‌های اطلاعاتی، دو مغزه رسوبی در محل های رفیع و جفیرتا عمق 10 متری به منظور تعیین رابطه بین قطر ذرات رسوبی با شرایط سیلابی و محیط های رسوب گذاری گرفته شد. نتایج نشان داد، سه توالی رسوبی با شرایط اقلیمی مرطوب و کاهش قطر ذرات رسوبی در اعماق(10-6، 5-4، 3-0 متری) و دو دوره با شرایط اقلیمی خشک به همراه افزایش قطر ذرات رسوبی در اعماق( 6-5 و 4-3 متری) را می توان در مغزه ها تشخیص داد. شرایط اقلیمی خشک به همراه عقب‌نشینی خط ساحلی در هولوسن میانی سبب شد، دلتای کارون و کرخه توسعه پیداکرده و جابجایی و تغییر مسیرهایی نیز در بستر این رودخانه ها پدیدار شود. این تغییرات در مسیر روستای عبدالخان تا تالاب هویزه دارای حداقل دو تغییر شکل پلان خم رودخانه و چندین مسیر متروکه طبیعی می باشد. به دلیل سرعت و تنش برشی، خم‌ها با پدیده انتقال وگسترش همراه بوده‌ و ضمن ایجاد خسارت به اراضی کشاورزی و مسکونی، موجب جابجایی آن ها نیز شده است.