River regulation cause unnatural water flow patterns which disrupt succession, survival and dispersal of riverine plant communities. Riparian zones in regulated rivers are generally more species poor and have a lower vegetation cover compared to free-flowing rivers. Tributary mouths within the impoundment however, are not only affected by processes in the main channel, but also affected by processes such as sediment dynamics and flooding regime from the tributary which may more reflect a natural regime and may therefore not be affected by hydropeaking to the same extent. Hence, tributary sites and the accompanied tributary mouths may represent hotspots for high diversity plant communities in regulated rivers. The riparian habitat is unique in its interaction with adjacent ecological systems and is therefore considered important for the riverine ecosystem’s ecological functioning. The aim of the study was to evaluate the significance of tributary sites and accompanied tributary mouths as a hotspot for diverse plant communities in regulated rivers. Additionally, geomorphological features were analyzed to access the impact of hydropeaking in sheltered and non-sheltered tributary sites. Data was acquired from sampling sites within the Umeå and Luleå rivers, representing both tributary mouths and non-tributary mouth reaches. Inventories included presence of riparian and aquatic vascular plant species, vegetation cover and soil composition. The results indicate a less extensive impact of hydropeaking in tributary mouths compared to non-tributary mouth reaches. The tributary mouths had a higher species richness, diversity and vegetation cover when compared to that of the non-tributary mouth reaches. This supports the concept of tributary mouths being hotspots for plant diversity. Moreover, the sheltered tributary mouths had a higher species richness than the non-sheltered tributary sites, suggesting tributary shelter as a contributing counter of hydropeaking effects.

This dissertation aims to improve our understanding of how dams and reservoirs impact freshwater systems worldwide. The following questions were addressed specifically: 1) what are the spatial patterns and magnitudes of flow regulation and channel fragmentation by dams globally; 2) how are dam impacts distributed biogeographically, and which are the biogeographic regions and taxa most threatened by dam impacts; and 3) how can climate change and dams be expected to interact in basins, and what management actions would mitigate adverse interactions? Results show that the majority of the world’s large river systems are fragmented and have their flow altered by dams. Exceptions to this tend to lie in regions inhospitable to hydropower development, such as northern tundra, or in the least economically active regions. The biogeographic distribution of dam impact is widespread, both at terrestrial and freshwater scales, representing significant threat to global biodiversity. Relatively species-poor tundra is the world’s only terrestrial ecoregion which remains predominantly unaffected by dams. Nearly half of the world’s freshwater ecoregions are internally fragmented by dams, and ecoregional distinctions may be artifically imposed by dams in many cases. Freshwater ecoregions with the highest counts of total and endemic species remain relatively unobstructed, representing significant conservation potential. Diadromy is one of the few fish traits indicative of vulnerability to dams for which data are sufficient for global scale analysis. Lampreys (Lampetra spp.), Eels (Anguilla spp.) and Shad (Alosa spp.) are examples of genera particularly vulnerable to dams because their distributions coincide with the most heavily fragmented freshwater ecoregions, and a large proportion of the coincident species for each genera are diadromous. Due to changes in discharge and water stress, the area of large river basins in need of management interventions to protect ecosystems or people will be much greater for basins impacted by dams than for basins with free-flowing rivers. Proactive measures that restore the natural capacity of rivers to buffer climate-change impacts are more desirable than reactive actions since they may also lead to environmental benefits such as higher water quality and restored fish populations – benefits which may later be unattainable.

Due to the impact of Taiwan geography and topography, flow rate in rivers goes up and down intensely with rainfall. Rivers are usually lack of dilution capacity, especially during dry season with little rainfall. Water quality has been damaged by untreated municipal wastewater, industrial wastewater and landfill leachate discharged into rivers through gutters, hidden pipes or tributaries discharger, especially obvious in metropolitan rivers. Love river is a typical metropolitan river. It has been under restoration by stages since 1977. Due to the lack of restoration in its upstream segments, this project is to analyze current water quality and to estimate pollutant loading through integration of related materials and documents in Love rivers, as well as to simulate water quality by WASP model through the analyses of measurement data for main and tributaries dischargers as the evaluation of pollution improvement action. Past water quality analyses shows that most upstream segments (upstream of sluicegate under water in Baozhu gutter) are between medium and serious polluted. In addition, results of water quality and flow rates in tributaries discharger shows that (River Pollution Index, RPI) in southern discharger left to Yucheng bridge, K trunk discharger and Baozhu gutter discharger are between 7.25 to 8.25, indicating that this tributaries discharger is the primary source for Lover river pollution. The objectives of this research are to lower the level of upstream pollution through the policies provided through related restoration experience before the sewage system for Kaohisung city is completely developed. As shown by the simulation of pollution reduction, through the combination of water interception and water injection, biochemical oxygen demand and ammonia nitrogen in water segments downstream of Dingxin bridge was reduced above 65% and 50%, respectively. The fact that water is discharged into Love river after purification by the combination of water interception and source water treated by water purification engineering is beneficial for the reduction of downstream biochemical oxygen demand and ammonia, as well as the improvement of dissolved oxygen to eventually meet the goal of lowering levels of water pollution. The Forecast results of the water quality model used in this study can evaluate the cost-efficiency of pollution reduction action and to provide priority restoration policy in the future as references in the following studies.

<p>Abstrakt: Jag har undersökt hur älvreglering påverkar mängden knott (Tvåvingar: <i>Simuliidae</i>) längs flera norrlandsälvar och vilka konsekvenser denna påverkan får för den landlevande fågelfaunan. Studien visar att utbyggnad av älvar har en negativ effekt på mängden knott. Det fanns sju gånger högre tätheter av knott längs "orörda älvar" jämfört med utbyggda älvar.</p><p>Skillnaden i antal knott mellan älvtyperna var mycket större för knotthanar än för knotthonor, vilket förklaras av att honorna är rörligare eftersom de flyger och letar efter blod. Knott lever av blod från ett flertal däggdjur och fåglar och visar en stor variation i värd-specificitet mellan olika arter. Jag fann en högre frekvens av haemosporida blod parasiter (<i>Leucocytozoon</i>) i fåglar längs "orörda" Vindelälven jämfört med den reglerade Umeälven. Detta mönster stämmer väl överens med tätheten fågelparasiterande knott som är lägre längs Umeälven. Knott attackerade främst värdar som var stora och vanliga. Fågelsamhällets sammansättning skiljde sig mellan orörda och utbyggda älvdalar. Tätheten av icke insektsätande fåglar tenderade att minska, efter häcksäsongen, längs orörda älvar medan den ökade längs utbyggda älvar. Den insektsätande fågeln svartvit flugsnappare (<i>Ficedula hypoleuca Pallas</i>) uppvisade större häckningsframgång längs orörda älvar jämfört med utbyggda älvar. Detta är förmodligen en effekt av den större mängden insekter som finns längs orörda älvar.</p> / <p>The effects of river regulation on blackfly (Diptera: <i>Simuliidae</i>) abundances and consequences for the avifauna in terrestrial environments were studied along multiple rivers in northern Sweden. I found that impoundment of rivers has detrimental effect to blackfly abundances. The densities of large-river breeding blackfly species were several-fold higher along free-flowing than along regulated rivers. The difference in abundances was much larger in males than blood-seeking females. Blackflies attacked a variety of mammalian and avian hosts and showed different levels of host-specificity between species. I found higher prevalence of haemosporidian blood parasites (<i>Leucocytozoon</i>) in birds along the free-flowing Vindel River in comparison to the regulated Ume River, where the lower densities of ornithophilic blackflies were reduced. Blood-seeking blackflies predominantly attacked large and/abundant hosts.</p><p>Assemblages of birds differed between valleys of regulated and free-flowing rivers. Densities of noninsectivorous birds tended to decrease along free-flowing rivers in the post-breeding season, but increased along regulated rivers at the same time. Insectivorous European pied flycatcher (<i>Ficedula hypoleuca Pallas</i>) showed greater fledging success along free-flowing than regulated rivers, which probably reflects the higher insect abundances found along freeflowing rivers.</p>

Abstrakt: Jag har undersökt hur älvreglering påverkar mängden knott (Tvåvingar: Simuliidae) längs flera norrlandsälvar och vilka konsekvenser denna påverkan får för den landlevande fågelfaunan. Studien visar att utbyggnad av älvar har en negativ effekt på mängden knott. Det fanns sju gånger högre tätheter av knott längs "orörda älvar" jämfört med utbyggda älvar. Skillnaden i antal knott mellan älvtyperna var mycket större för knotthanar än för knotthonor, vilket förklaras av att honorna är rörligare eftersom de flyger och letar efter blod. Knott lever av blod från ett flertal däggdjur och fåglar och visar en stor variation i värd-specificitet mellan olika arter. Jag fann en högre frekvens av haemosporida blod parasiter (Leucocytozoon) i fåglar längs "orörda" Vindelälven jämfört med den reglerade Umeälven. Detta mönster stämmer väl överens med tätheten fågelparasiterande knott som är lägre längs Umeälven. Knott attackerade främst värdar som var stora och vanliga. Fågelsamhällets sammansättning skiljde sig mellan orörda och utbyggda älvdalar. Tätheten av icke insektsätande fåglar tenderade att minska, efter häcksäsongen, längs orörda älvar medan den ökade längs utbyggda älvar. Den insektsätande fågeln svartvit flugsnappare (Ficedula hypoleuca Pallas) uppvisade större häckningsframgång längs orörda älvar jämfört med utbyggda älvar. Detta är förmodligen en effekt av den större mängden insekter som finns längs orörda älvar. / The effects of river regulation on blackfly (Diptera: Simuliidae) abundances and consequences for the avifauna in terrestrial environments were studied along multiple rivers in northern Sweden. I found that impoundment of rivers has detrimental effect to blackfly abundances. The densities of large-river breeding blackfly species were several-fold higher along free-flowing than along regulated rivers. The difference in abundances was much larger in males than blood-seeking females. Blackflies attacked a variety of mammalian and avian hosts and showed different levels of host-specificity between species. I found higher prevalence of haemosporidian blood parasites (Leucocytozoon) in birds along the free-flowing Vindel River in comparison to the regulated Ume River, where the lower densities of ornithophilic blackflies were reduced. Blood-seeking blackflies predominantly attacked large and/abundant hosts. Assemblages of birds differed between valleys of regulated and free-flowing rivers. Densities of noninsectivorous birds tended to decrease along free-flowing rivers in the post-breeding season, but increased along regulated rivers at the same time. Insectivorous European pied flycatcher (Ficedula hypoleuca Pallas) showed greater fledging success along free-flowing than regulated rivers, which probably reflects the higher insect abundances found along freeflowing rivers.

A l’image du Rhône au sud-est de la France, les fleuves font l’objet de multiples usages, entrainant des modifications profondes de leurs dynamiques fluviales. Par conséquent, les fonctionnements hydro-sédimentaire et écologique de leurs chenaux ainsi que de leurs plaines alluviales sont altérés. Des programmes intégrés de restauration s’attellent à définir les potentiels et les risques liés à de tels ‘écosystèmes anthropo-construits’ et de comprendre les interactions entre divers facteurs de contrôle ayant influencé leur formation. La présente étude s’est focalisée sur 293 casiers Girardon – des unités rectangulaires délimitées par des digues submersibles longitudinales et latérales construites dans le lit mineur au 19ème siècle afin d’améliorer la navigabilité du Rhône. Ceux-ci sont distribués sur quatre secteurs court-circuités au 20ième siècle pour la production hydro-électrique. Nous avons analysé les patrons spatio-temporels de la sédimentation, ainsi que la structure et la composition des boisements grâce à des données issues de la télédétection et de terrain. Nous proposons également un modèle conceptuel des facteurs de contrôle et des processus potentiels en lien avec les patrons observés. Quatre-vingts pourcents des casiers ont évolué du stade aquatique à un stade terrestre et boisé, suivant des trajectoires historiques variées à la fois inter- et intra-secteurs. Les boisements diffèrent en caractéristiques structurelles de boisements de référence plus naturels. Leur composition est plus proche de celle des systèmes matures que pionniers. Nous observons également une forte présence d’espèces allochtones, comme par exemple l’Érable negundo (Acer negundo), invasive, en particulier dans les stades de régénération. Notre approche comparative constitue une première étape pour démêler les effets cumulatifs des facteurs de contrôle et hiérarchiser leurs rôles individuels. Nous avons constaté que des facteurs locaux jouent un rôle majeur, en particulier la connectivité au chenal principal court-circuité. L’évolution des facteurs environnementaux eux-mêmes a contribué à la complexité des patrons. Ce travail ouvre la voie à des futures études sur des écosystèmes anthropo-construits sur cours d’eau, et donne une nouvelle perspective aux gestionnaires du Rhône relativement à son échelle spatiale innovante. / The multiple uses made of large rivers, such as the Rhône in south-eastern France, have provoked profound modifications of their fluvial dynamics. As a consequence, the hydro-sedimentary and ecological functioning of their channels and floodplains are highly altered. Integrated restoration programmes struggle in defining potentials and risks related to such ‘novel ecosystems’ and to understand the various interacting drivers which influence their formation. This study comparatively focused on 293 dike fields—rectangular units delimited by longitudinal and lateral submersible dikes constructed in the channel in the late 19th century to promote the navigability of the Rhône. They are distributed over four reaches by-passed in the 20th century for hydro-electric energy production. We investigated the spatio-temporal patterns of sediment deposition and the structure and composition of the forest stands using remote sensing and field data. We also propose a conceptual model of potential drivers and processes behind the observed patterns. Eighty percent of the dike fields have evolved from the aquatic to a terrestrial and forested stage, following variable historical trajectories both between and within reaches. The forest stands presented structural characteristics which differed from more natural reference stands and compositional characteristics closer to mature than to pioneer systems. They featured a high presence of non-native species, such as the invasive Box elder (Acer negundo). Our comparative approach constituted a first step to disentangle the cumulative effects of the drivers and define their individual roles: we discovered a prominent role of local factors, especially the connectivity to the main by-passed channel. The evolution of the environmental factors themselves added to the complexity of the patterns. This work provides a basis for future studies of novel ecosystems on rivers, and a new perspective to river managers on the Rhône due to its innovative spatial-scale.

Regulation of the Upper Tombigbee River and its incorporation into the Tennessee-Tombigbee Waterway has resulted in main-channel flows that differ from the pre-regulation condition. Flows differ in (1) magnitude: higher base flows, damped peak flows, and (2) variability: the river rises and falls faster and the number of reversals has increased. A shift in the trophic ecology of the resident fish assemblage corresponded with the altered hydrology. Assemblage-level trophic plasticity manifested through dietary shifts in species present during both time periods are coupled with changes to the taxonomic structure observed previously. Species representing the contemporary assemblage feed on fewer taxa regardless of respective trophic ecologies and include taxa that are not characteristic of diets under pre-regulation conditions. More basal resources contributing to production resulted in a greater number of trophic pathways flowing through a decreased dietary breadth. Reduced foraging efficiency is inferred for riverine specialists, possibly resulting in lower fitnesses. Tributaries are highlighted as important in maintaining biodiversity in the regulated main-channel because flows and associated trophic ecologies of resident fishes are relatively similar to those observed under pre-regulation conditions. Materials and taxa exhibit unique interactions at “zones of confluence” where unregulated tributaries merge with the main-channel. Quantifiable characteristics of trophic ecology and ecomorphology, along with connectance to free flowing major tributaries, emerge as potential indicators of the vulnerability of fishes to hydrologic alteration.

From the Proceedings of the 1975 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 11-12, 1975, Tempe, Arizona / The importance of water resources and an increasing interest on improvement of out environment have identified the urgent need for methods to predict river response due to various changes resulting from proposed water resource planning. Fluvial geomorphology and hydraulic elements that are related to the interpretation and modeling of response to the problem are presented. Interpretation of alluvial rivers should be preceded by a qualitative analysis and information is presented which should be adequate to carry this out in most cases. This should be followed by a quantitative evaluation of channel response and water sediment routing using theory supplemented by physical and mathematical model studies of the system.

The effects of climate and environmental change are likely to exacerbate water stress in Africa over the next five decades. It appears obvious, therefore, that large river basins with considerable total renewable water resources will play a prominent role in regional cooperation to alleviate the pressure of water scarcity within Africa. However, managing water resources in the large river basins of Africa involves problems of data paucity, lack of technical resources and the sheer scale of the problem. These river basins are located in regions that are characterized by poverty, low levels of economic development and little food security. The rivers provide multiple goods and services that include hydro-power, water supply, fisheries, agriculture, transportation, and maintenance of aquatic ecosystems. Sustainable water resources management is a critical issue, but there is almost always insufficient data available to formulate adequate management strategies. These basins therefore represent some of the best test cases for the practical application of the science associated with the Predictions in Ungauged Basins (PUB). The thesis presents the results of a process-based hydrological modelling study in the Congo Basin. One of the primary objectives of this study was to establish a hydrological model for the whole Congo Basin, using available historical data. The secondary objective of the study was to use the model and assess the impacts of future environmental change on water resources of the Congo Basin. Given the lack of adequate data on the basin physical characteristics, the preliminary work consisted of assessing available global datasets and building a database of the basin physical characteristics. The database was used for both assessing relationships of similarities between features of physiographic settings in the basin (Chapters 3 and 4), and establishing models that adequately represent the basin hydrology (Chapters 5, 6, and 7). The representative model of the Congo Basin hydrology was then used to assess the impacts of future environmental changes on water resources availability of the Congo Basin (Chapter 8). Through assessment of the physical characteristics of the basin, relationships of similarities were used to determine homogenous regions with regard to rainfall variability, physiographic settings, and hydrological responses. The first observation that comes from this study is that these three categories of regional groups of homogenous characteristics are sensible with regards to their geographical settings, but the overlap and apparent relationships between them are weak. An explanation of this observation is that there are insufficient data, particularly associated with defining sub-surface processes, and it is possible that additional data would have assisted in the discrimination of more homogenous groups and better links between the different datasets. The model application in this study consisted of two phases: model calibration, using a manual approach, and the application of a physically-based a priori parameter estimation approach. While the first approach was designed to assess the general applicability of the model and identify major errors with regard to input data and model structure, the second approach aimed to establish an understanding of the processes and identify useful relationships between the model parameters and the variations in real hydrological processes. The second approach was also designed to quantify the sensitivity of the model outputs to the parameters of the model and to encompass information sharing between the basin physical characteristics and quantifying the parameters of the model. Collectively, the study’s findings show that these two approaches work well and are appropriate to represent the real hydrological processes of Congo Basin. The secondary objective of this study was achieved by forcing the hydrological model developed for the Congo Basin with downscaled Global Climate Model (GCMs) data in order to assess scenarios of change and future possible impacts on water resources availability within the basin. The results provide useful lessons in terms of basin-wide adaptation measures to future climates. The lessons suggest that there is a risk of developing inappropriate adaptation measures to future climate change based on large scale hydrological response, as the response at small scales shows a completely different picture from that which is based on large scale predictions. While the study has concluded that the application of the hydrological model has been successful and can be used with some degree of confidence for enhanced decision making, there remain a number of uncertainties and opportunities to improve the methods used for water resources assessment within the basin. The focus of future activities from the perspective of practical application should be on improved access to data collection to increase confidence in model predictions, on dissemination of the knowledge generated by this study, and on training in the use of the developed water resources assessment techniques.

RESUMEN Los peces nativos son indicadores de la salud de los ecosistemas acuáticos, y se han convertido en un elemento de calidad clave para evaluar el estado ecológico de los ríos. La comprensión de los factores que afectan a las especies nativas de peces es importante para la gestión y conservación de los ecosistemas acuáticos. El objetivo general de esta tesis es analizar las relaciones entre variables biológicas y de hábitat (incluyendo la conectividad) a través de una variedad de escalas espaciales en los ríos Mediterráneos, con el desarrollo de herramientas de modelación para apoyar la toma de decisiones en la restauración de ríos. Esta tesis se compone de cuatro artículos. El primero tiene como objetivos modelar la relación entre un conjunto de variables ambientales y la riqueza de especies nativas (NFSR), y evaluar la eficacia de potenciales acciones de restauración para mejorar la NFSR en la cuenca del río Júcar. Para ello se aplicó un enfoque de modelación de red neuronal artificial (ANN), utilizando en la fase de entrenamiento el algoritmo Levenberg-Marquardt. Se aplicó el método de las derivadas parciales para determinar la importancia relativa de las variables ambientales. Según los resultados, el modelo de ANN combina variables que describen la calidad de ribera, la calidad del agua y el hábitat físico, y ayudó a identificar los principales factores que condicionan el patrón de distribución de la NFSR en los ríos Mediterráneos. En la segunda parte del estudio, el modelo fue utilizado para evaluar la eficacia de dos acciones de restauración en el río Júcar: la eliminación de dos azudes abandonados, con el consiguiente incremento de la proporción de corrientes. Estas simulaciones indican que la riqueza aumenta con el incremento de la longitud libre de barreras artificiales y la proporción del mesohabitat de corriente, y demostró la utilidad de las ANN como una poderosa herramienta para apoyar la toma de decisiones en el manejo y restauración ecológica de los ríos Mediterráneos. El segundo artículo tiene como objetivo determinar la importancia relativa de los dos principales factores que controlan la reducción de la riqueza de peces (NFSR), es decir, las interacciones entre las especies acuáticas, variables del hábitat (incluyendo la conectividad fluvial) y biológicas (incluidas las especies invasoras) en los ríos Júcar, Cabriel y Turia. Con este fin, tres modelos de ANN fueron analizados: el primero fue construido solamente con variables biológicas, el segundo se construyó únicamente con variables de hábitat y el tercero con la combinación de estos dos grupos de variables. Los resultados muestran que las variables de hábitat son los ¿drivers¿ más importantes para la distribución de NFSR, y demuestran la importancia ecológica de los modelos desarrollados. Los resultados de este estudio destacan la necesidad de proponer medidas de mitigación relacionadas con la mejora del hábitat (incluyendo la variabilidad de caudales en el río) como medida para conservar y restaurar los ríos Mediterráneos. El tercer artículo busca comparar la fiabilidad y relevancia ecológica de dos modelos predictivos de NFSR, basados en redes neuronales artificiales (ANN) y random forests (RF). La relevancia de las variables seleccionadas por cada modelo se evaluó a partir del conocimiento ecológico y apoyado por otras investigaciones. Los dos modelos fueron desarrollados utilizando validación cruzada k-fold y su desempeño fue evaluado a través de tres índices: el coeficiente de determinación (R2 ), el error cuadrático medio (MSE) y el coeficiente de determinación ajustado (R2 adj). Según los resultados, RF obtuvo el mejor desempeño en entrenamiento. Pero, el procedimiento de validación cruzada reveló que ambas técnicas generaron resultados similares (R2 = 68% para RF y R2 = 66% para ANN). La comparación de diferentes métodos de machine learning es muy útil para el análisis crítico de los resultados obtenidos a través de los modelos. El cuarto artículo tiene como objetivo evaluar la capacidad de las ANN para identificar los factores que afectan a la densidad y la presencia/ausencia de Luciobarbus guiraonis en la demarcación hidrográfica del Júcar. Se utilizó una red neuronal artificial multicapa de tipo feedforward (ANN) para representar relaciones no lineales entre descriptores de L. guiraonis con variables biológicas y de hábitat. El poder predictivo de los modelos se evaluó con base en el índice Kappa (k), la proporción de casos correctamente clasificados (CCI) y el área bajo la curva (AUC) característica operativa del receptor (ROC). La presencia/ausencia de L. guiraonis fue bien predicha por el modelo ANN (CCI = 87%, AUC = 0.85 y k = 0.66). La predicción de la densidad fue moderada (CCI = 62%, AUC = 0.71 y k = 0.43). Las variables más importantes que describen la presencia/ausencia fueron: radiación solar, área de drenaje y la proporción de especies exóticas de peces con un peso relativo del 27.8%, 24.53% y 13.60% respectivamente. En el modelo de densidad, las variables más importantes fueron el coeficiente de variación de los caudales medios anuales con una importancia relativa del 50.5% y la proporción de especies exóticas de peces con el 24.4%. Los modelos proporcionan información importante acerca de la relación de L. guiraonis con variables bióticas y de hábitat, este nuevo conocimiento podría utilizarse para apoyar futuros estudios y para contribuir en la toma de decisiones para la conservación y manejo de especies en los en los ríos Júcar, Cabriel y Turia. / Olaya Marín, EJ. (2013). Ecological models at fish community and species level to support effective river restoration [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28853