Water resource management operations have significantly modified river flow regimes globally, prompting widespread lotic ecosystem responses. There is a growing need to better understand how increasingly prevalent hydrological alterations to riverine systems will affect biota dependent on specific elements of river flow regimes. This thesis examines macroinvertebrate community responses to river flow regimes modified by various water resource management operations across southwest England though four detailed investigations. The first study examines the influence of river impoundments and how macroinvertebrate communities differ between regulated and non-regulated sections of river. Findings from this investigation highlight that flow regulation alters the structure and function of faunal assemblages due to significant changes to the flow regime, rather than stream temperature modifications associated with the reservoirs. The second study focusses on groundwater dominated headwater streams transitioning from temporary (i.e. reaches periodically drying positioned furthest upstream) to perennial flow conditions which are subjected to variable groundwater abstraction intensities. The results indicate that macroinvertebrate communities respond significantly to the duration of antecedent flowing conditions and the spatial proximity of sampling sites to perennial sources; but faunal assemblages are not sensitive to groundwater abstraction. The third study examines how communities inhabiting different organic and mineralogical lotic habitats responded to multiple river flow properties (hydrological indices, anthropogenic flow alteration measures and hydraulic variables) in perennial, groundwater dominated systems. The findings highlight that faunal assemblages are most responsive to local hydraulic conditions measured at the point of sampling, rather than antecedent hydrological conditions. The influence of hydraulic properties on communities differs between lotic habitats, highlighting that mineralogical and organic characteristics of riverbeds strongly mediate how biota respond to flow. The final study presents the results of a long-term (1995-2016), region-wide (spanning Dorset, Hampshire and Wiltshire) examination of macroinvertebrate communities inhabiting groundwater dominated rivers and their responses to hydrological variability (including extreme low- and high-flow events) and anthropogenic flow alterations. The results indicate that indices characterising the proportion of discharge added to (through effluent water returns and low-flow alleviation strategies) or removed from the river (via groundwater abstraction) exert profound effects on faunal assemblages over long-term periods. These results provide empirical evidence that reductions in river discharges via groundwater abstraction of approximately 15% have no perceptible negative ecological effects on macroinvertebrate communities. The results from the four detailed investigations are used to develop conceptual models to illustrate how research undertaken within this thesis can be applied more widely. The findings and study designs presented within this thesis could inform surface and groundwater water resource management operations and underpin the development of environmental flow methodologies required to conserve riverine ecosystems globally.

The life history and ecology of Neochoroterpes mexicanus was studied from data collected September, 1971, to August, 1972, and January to December, 1973, in the Brazos River, Texas. Nymphal development, instar analysis, voltinism, standing crops, and production estimates were determined from the quantitative samples taken in 1971 and 1972. Aspects of the life history and food habits of 230 specimens were arrived at from qualitative samples and light box captures in 1973. Laboratory investigation in 1973 helped in establishing instar analysis, egg incubation and description, and first instar descriptions. Neochoroterpes mexicanus appeared to have three generations per year with brood overlap in the summer and fall. It displayed 16 and 19 instars for overwintering and combined summer generations respectively.

Effects of artificial water fluctuations called hydropeaking on the detachment rates of adhesive eggs were studied using a rheophlic fish (asp Leuciscus aspius) as a model species. I attempted to relate egg density to abiotic conditions of the spawning ground and identify optimal conditions for the eggs. Egg densities were also studied during spawning season when hydropeaking occurred. In the experimental setup, egg detachment rates were tested with different speeds, substrate type and exposition time and critical conditions for the eggs were assessed.

1. Large rivers in the central United States experience a variety of ecological interactions. Both short- and long-term temporal changes affect both fish and zooplankton communities in rivers. Variation in diel patterns of predation could affect differences of behavior in prey. Long term temporal changes across seasons can lead to different areas of rivers providing growth or costing energy. Spatial changes also affect habitat quality and behaviors of the aquatic organisms within large rivers. Spatial variation can be dynamic and occur between longitudinally connected habitats or vary through different sections of the reach and can also change seasonally. 2. Invasive species have major economic and ecological impacts. In aquatic ecosystems, plankton are the base of the food web and a planktivore invader can cause major ecological disruptions. The Wabash River is a large free flowing river with a variable hydrology, which causes dramatic changes in habitat availability through time. Therefore, habitat usage, quality, and availability may differ for native and invasive species through time. The objectives of this study were to assess how habitat quality changes in a large, flashy, free-flowing river over time, and to compare the quantity and overlap of quality macrohabitat for invasive and native fish. Growth rate potential (GRP) was used to quantify habitat quality for Silver Carp (Hypophthalmichthys molitrix; invasive) and Gizzard Shad (Dorosoma cepedianum; native). To calculate GRP, bioenergetic models were used with monthly observations of food abundance (zooplankton, phytoplankton, and detritus), water temperature, dissolved oxygen, and water velocity of various habitat types from the Wabash River’s confluence with the Ohio River upstream to Terre Haute, Indiana, approximately 215 river miles. Negative GRP for both Silver Carp and Gizzard Shad occurred during spring and most of summer. However, in the fall, the majority of the river had a positive GRP for both species. Reduced flows and increases in food abundance were the cause for the switch from negative to positive GRP. There was a high degree of spatial overlap in positive GRP areas between Silver Carp and Gizzard Shad, suggesting that there is a high degree of competition. Acoustically tagged Silver Carp selected for areas predicted to have a positive GRP from the model presented in the study. This model showed that regulation of flows in hydrologically altered systems could potentially lower the impact of Silver Carp in those systems. With Silver Carp selecting for predicted habitats, a bioenergetics model can be used to inform commercial fishers where to focus effort to maximize catch.3. Temporal changes in rivers tend to be quantified at broad seasonal scales. However, river conditions including water flow, water temperature, dissolved oxygen, and availability of zooplankton prey may change daily. In large rivers, these conditions may change in a diel fashion between backwater and main channel habitats. To assess diel changes in the Illinois River, zooplankton, paired with mobile hydroacoustic surveys for fish were sampled from three main channel and three off-channel sites in the LaGrange reach every four hours in a twenty-four-hour period at different depths between October 22 and 26, 2018. Water depth, water temperature, water velocity, and fish (planktivore and nonplanktivore) densities were quantified during each sampling time. Water temperature and water velocity differed between the two habitat types. Water temperature was higher and water velocity was lower in the off-channel. Water temperature was colder in the morning in both the main channel and off-channel. Water velocity did not change throughout the day. The majority of the zooplankton community was comprised of rotifers which were less mobile than larger taxa and did not migrate. When evaluating the more mobile, large body zooplankton, time and depth affected copepod density in off-channel environments, where the deeper depth had a higher copepod density than the shallower depth. In contrast, only time of day affected off-channel cladoceran density, where densities increased at night. Fish did not exhibit diel patterns and the off-channel habitat had a higher density. The most likely mechanism behind the diel movements of the large bodied zooplankton was predation by planktivorous fish. The present study suggests that connections to the off-channel habitats in large rivers will promote quality habitat for both zooplankton and fish.

Genetic variation and thermal tolerance were surveyed for variation attributed to nonuniform selection pressures for five populations of the red shiner, Notropis lutrensis, collected from regulated and unregulated portions of a Texas river. Populations within 30 km of a hypolimnion-release dam that experience large thermal perturbations were found to have higher levels of heterozygosity, higher levels of polymorphism, significantly depressed levels of upper thermal tolerance endpoints, and greater variances in tolerance endpoints. These populations have evolved enzyme systems differing from the unregulated populations in response to a variable and depressed thermal regime.

Os estudos em microbacias hidrográficas têm mostrado que as características físicas, químicas e biológicas das águas dos córregos e riachos possuem uma estreita relação com a composição do ambiente terrestre adjacente, refletindo as condições de uso e ocupação dos solos da bacia hidrográfica por eles drenada. A microbacia do Córrego do Cancã, localizada perpendicularmente ao Rio Monjolinho, situa-se em uma maior parte no município de São Carlos (SP), e foi estudada sob uma abordagem ecossistêmica. As coletas e análises de campo foram realizadas em sete transectos do córrego, em dois períodos hidrológicos distintos: seca e chuva. A caracterização física e química da água foi realizada através da análise do pH, da condutividade elétrica, da concentração de oxigênio, da temperatura, da concentração e da carga de nutrientes. Alguns dos parâmetros analisados foram comparados aos limites estabelecidos pela CONAMA segundo a resolução nº 20/1986. O córrego do Cancã, segundo a classificação proposta pela CONAMA, é um rio de classe-2. A água do córrego é levemente ácida tendendo à neutralidade em um gradiente da nascente à foz e caracteriza-se pela baixa condutividade elétrica. A temperatura variou entre os períodos avaliados e espacialmente foi influenciada pelos horários de coleta. As concentrações de nutrientes não foram elevadas, e das formas nitrogenadas as mais abundantes foram o nitrato (na estação mais impactada) e o amônio (após o represamento), com valores mais elevados no período de seca. A maior variabilidade foi observada para o nitrogênio total, sendo as maiores concentrações registradas na estação seca. Com base no índice de estado trófico, as águas do córrego do Cancã foram classificadas como mesotróficas. A forma da microbacia é irregular e ligeiramente alongada e pouco sujeita a enchentes. A área da microbacia foi determinada como sendo de 3,075 Km2. Na análise das comunidades planctônicas foram encontrados poucos representantes, distribuídos principalmente nas estações localizadas nos trechos inicial e médio do córrego, sendo, entretanto mais abundantes na nascente. Ocorreu predominância das clorofíceas e diatomáceas entre os organismos fitoplanctônicos e de rotíferos e cladóceros no zooplâncton. A microbacia está sujeita à práticas agrícolas e atividade pecuária semi-intensiva que alteram o balanço de massa dos principais nutrientes, contribuindo para o aumento da carga de nutrientes que são carreados do sistema terrestre para o aquático particularmente no período chuvoso. / The studies peformed in small hydrographic basins have shown that the physical chemical and biological characteristics of the water in springs and streams have a close relation with the composition of adjacent terrestrial ecosystems, reflecting the uses and activities in the soils in the basin drained by them. The microbasin of Cancã stream belongs to the Monjolinho river basin and is mainly located inside the district of São Carlos (SP). In this study It has been evaluated under the ecosystemic approach. Field sampling and analysis were carried out in seven transects of the stream at two distinct hydrological periods: dry and rainy seasons. Physical and chemical analyses of water were performed by mesuring the pH, electrical conductivity, dissolved oxygen and the nutrient concentrations and loads. The parameters obtained were compared to the CONAMA limits, act nº 20/1986. The Cancã stream according to CONAMA proposed system, is classified as a class 2 water. The pH of Cancã water is slightly acid and there a tendency to the neutral from the source to the mouse. It is also characterized by low electrical conductivity. Water temperature has changed between dry and rainy periods and spatially it was influenced by the sampling timing. Nutrient concentrations are low and the main nitrogen compounds present were nitrate and ammonium, at the most impacted site, with highest values in the dry season. The highest variability was obtained for the total nitrogenvariability with higher concentrations at the dry season. Based on the trophic state index. The water of Cancã stream was classified as mesotrophic. The hydrographic microbasin has a non-regular shape, being slightly elongated and it has low vulnerability to floodings. The area of the catchment was found to be 3,071 Km2. Planktonic communities were composed by few organisms mainly occuring at the upper and middle stream streches, being most abundant at the first stretch. Clorophyceans and diatoms were the dominant groups among phytoplankton and the rotifers and cladocerans among the zooplankton. Cancã microbasin is subjected to a variety of agriculture and semi-intensive cattle enterprises that have changed major nutrient mass balances, contributing to the increase in nutrient loadings mainly via surface terrestrial runoff.

Os sistemas lóticos são considerados sistemas abertos e de fluxo unidirecional de energia. Nestes sistemas a intensa relação com o meio terrestre adjacente faz com que as condições ecológicas dos rios sejam um reflexo das transformações ocorridas em sua bacia de drenagem. O objetivo do presente estudo foi traçar um perfil dos aspectos ecológicos do rio Uberaba-MG, em função dos usos preponderantes da bacia hidrográfica. Foram avaliadas as características limnológicas, a comunidade de macroinvertebrados bentônicos e o estado de conservação da área de entorno do rio. Procurou-se ainda avaliar a evolução espacial e a variação temporal das variáveis mensuradas à luz de teorias ecológicas de sistemas lóticos. Os resultados mostraram que no rio Uberaba três zonas com impactos preponderantes, diferentes, devem ser avaliadas com maior cautela: a) antes do município de Uberaba existe a predominância de atividades agrícolas, que promovem impactos pela entrada contínua de sedimentos e oferecem riscos pela entrada de agrotóxicos e fertilizantes, b) abaixo do município de Uberaba, a entrada de efluentes gera acentuada degradação da qualidade da água e o conseqüente perecimento das comunidades biológicas, até a região próxima ao município de Veríssimo, e c) a região compreendida entre os municípios de Veríssimo, Conceição das Alagoas e Planura, pelo crescente risco de degradação da qualidade da água decorrente da entrada de efluentes e do aumento do desmatamento nas margens do rio Uberaba e afluentes. Discute-se ainda a necessidade de serem aprimoradas teorias ecológicas para sistemas lóticos tropicais, com o intuito de aumentar a capacidade de predição sobre este sistema e remeter estratégias de conservação mais eficientes aos gestores ambientais. / Lotic systems are considered opened and one-way energy flux systems. In these cases, the intense relationship with adjacent terrestrial environment renders rivers ecological conditions a reflex of transformations occurred at its watershed. The present study aimed to profile an Uberaba river ecological features as a function of the watershed main uses. Limnological characteristic, benthic macroinvertebrates community and conditions at river nearby area were evaluated. Based on the lotic systems ecological theories, it was attempted to evaluate the measured variable space evolution and temporal variation. Results showed that in Uberaba river, three zones with different impacts should be carefully evaluated: a) before Uberaba city, agricultural activities predominates, promoting impacts due to the continuous sediment input, and offering risks of pesticide and fertilizers contribuition; b) below Uberaba city, wastewater effluent generates high water quality degradation, resulting in biological communities decay until the area closed to Veríssimo City; and c) at the region embracing Veríssimo, Conceição das Alagoas and Planura cities, in function of the growing water quality degradation risk due to effluents entrance and deforesting increase at the margins of Uberaba river and tributaries. The needs of improved ecological theories for tropical lotic systems are also discussed, aiming to increase the prediction capacity on this lotic systems and to transmit more efficient conservation strategies to environmental managers.

Large scale ecosystem restoration is an important societal issue because significant risks, costs, and benefits can accrue on large landscapes. It is important to understand baseline ecosystem conditions, existing condition, and to the extent possible estimate ecosystem response to alternative management scenarios. Incorporating ecosystem process and function into restoration planning and implementation will make ecosystem restoration projects sustainable. The Upper Mississippi River System is an excellent case study for such issues because it is an important, multiple-use ecosystem with significant ongoing investment in ecosystem, agri-system, and navigation system management. Large-scale geomorphology, hydrology, and land cover information was compared among presettlement, contemporary, and potential future reference conditions to examine ecosystem state and evaluate mechanisms responsible for ecosystem condition. The UMRS was scaled by physiographically similar characteristics into large floodplain reaches several hundred river miles in length, geomorphic reaches 50 to several hundred miles, and a mile-by-mile segmentation of the river floodplain extent. Ecologically relevant geomorphic classes were devised from existing data and evaluated by river reach to characterize presettlement geomorphology, and dams and levees were superimposed to reflect the altered hydrogeomorphology of the contemporary ecosystem. A pre- and post-impact Indicators of Hydrologic Alteration river stage analysis evaluated dam impacts, and pre-dam and post-dam aquatic habitat class distribution was compared. A floodplain inundation simulation analysis provided new information on the potential spatial distribution of frequent floods. Land cover data available for presettlement and modern reference periods were compared at several spatial scales. Multivariate analyses evaluated land cover characteristics among geomorphic reaches, as well as to assess the influence of hydrogeomorphic drivers on land cover for presettlement and contemporary reference periods. The objective of this research was to clearly delineate the divergence of environmental conditions among reference periods to evaluate which drivers need to be, and can be, altered to change ecosystem state. Hydrogeomorphic response to development indicates several restoration objectives that are appropriate system-wide and others that are best suited to specific river reaches. Similar data sources are available for much of the rest of the United States through the Public Land Survey and engineering surveys of any significant civil works projects.

The planning and management of coastal and river structures such as breakwaters, groynes, jetties, bridges and tidal inlets require accurate predictions of equilibrium morphologies. Generally these types of situations are modelled numerically using process - based models, where wave, current and sediment transport modules are applied over a number of time - steps until a steady - state morphology is obtained. Two alternative methods have been developed and applied in this thesis, based on self - organisation and entropy approaches. The self - organisation - based method utilises a cellular automata model, where local rules produce a global stable pattern through positive and negative feedback. The entropy - based method is able to predict equilibrium morphologies directly. It compares different randomly generated morphologies using an objective function and optimisation, instead of moving to an equilibrium morphology through intermediate states. This avoids some potential problems associated with traditional models such as error propagation and reliance on accurate initial conditions. The models developed in this thesis have been applied to a number of case studies. It was found that the cellular automata model obtained a higher Brier Skill Score than a comparable process - based model when predicting the equilibrium morphology associated with a channel obstruction. The entropy - based method was able to predict a realistic erosional channel in a coastal lagoon, similar to field observations at the Murray River Mouth in South Australia. It had difficulties predicting the deposition pattern due to the bias of the objective function towards erosional environments. The entropy - based method outperformed a conventional model prediction of the equilibrium erosional channel associated with a laboratory - sized lagoon, but similar problems were observed with its deposition predictive ability. The modelling methods developed in this thesis are a first step into the use of non - traditional, entropy - and self - organisation - based models for the prediction of complex equilibrium morphologies. They have made use of non - conventional models in order to explore different objective function formulations or self - organisation rules and the sensitivity of these, and have compared the models to laboratory results. The work documented in this dissertation shows that it is possible to use self - organisation - and entropy - based modelling methods to predict stable, equilibrium morphologies in coastal and river environments. / Thesis (Ph.D.)--School of Civil and Environmental Engineering, 2006.

Os estudos em microbacias hidrográficas têm mostrado que as características físicas, químicas e biológicas das águas dos córregos e riachos possuem uma estreita relação com a composição do ambiente terrestre adjacente, refletindo as condições de uso e ocupação dos solos da bacia hidrográfica por eles drenada. A microbacia do Córrego do Cancã, localizada perpendicularmente ao Rio Monjolinho, situa-se em uma maior parte no município de São Carlos (SP), e foi estudada sob uma abordagem ecossistêmica. As coletas e análises de campo foram realizadas em sete transectos do córrego, em dois períodos hidrológicos distintos: seca e chuva. A caracterização física e química da água foi realizada através da análise do pH, da condutividade elétrica, da concentração de oxigênio, da temperatura, da concentração e da carga de nutrientes. Alguns dos parâmetros analisados foram comparados aos limites estabelecidos pela CONAMA segundo a resolução nº 20/1986. O córrego do Cancã, segundo a classificação proposta pela CONAMA, é um rio de classe-2. A água do córrego é levemente ácida tendendo à neutralidade em um gradiente da nascente à foz e caracteriza-se pela baixa condutividade elétrica. A temperatura variou entre os períodos avaliados e espacialmente foi influenciada pelos horários de coleta. As concentrações de nutrientes não foram elevadas, e das formas nitrogenadas as mais abundantes foram o nitrato (na estação mais impactada) e o amônio (após o represamento), com valores mais elevados no período de seca. A maior variabilidade foi observada para o nitrogênio total, sendo as maiores concentrações registradas na estação seca. Com base no índice de estado trófico, as águas do córrego do Cancã foram classificadas como mesotróficas. A forma da microbacia é irregular e ligeiramente alongada e pouco sujeita a enchentes. A área da microbacia foi determinada como sendo de 3,075 Km2. Na análise das comunidades planctônicas foram encontrados poucos representantes, distribuídos principalmente nas estações localizadas nos trechos inicial e médio do córrego, sendo, entretanto mais abundantes na nascente. Ocorreu predominância das clorofíceas e diatomáceas entre os organismos fitoplanctônicos e de rotíferos e cladóceros no zooplâncton. A microbacia está sujeita à práticas agrícolas e atividade pecuária semi-intensiva que alteram o balanço de massa dos principais nutrientes, contribuindo para o aumento da carga de nutrientes que são carreados do sistema terrestre para o aquático particularmente no período chuvoso. / The studies peformed in small hydrographic basins have shown that the physical chemical and biological characteristics of the water in springs and streams have a close relation with the composition of adjacent terrestrial ecosystems, reflecting the uses and activities in the soils in the basin drained by them. The microbasin of Cancã stream belongs to the Monjolinho river basin and is mainly located inside the district of São Carlos (SP). In this study It has been evaluated under the ecosystemic approach. Field sampling and analysis were carried out in seven transects of the stream at two distinct hydrological periods: dry and rainy seasons. Physical and chemical analyses of water were performed by mesuring the pH, electrical conductivity, dissolved oxygen and the nutrient concentrations and loads. The parameters obtained were compared to the CONAMA limits, act nº 20/1986. The Cancã stream according to CONAMA proposed system, is classified as a class 2 water. The pH of Cancã water is slightly acid and there a tendency to the neutral from the source to the mouse. It is also characterized by low electrical conductivity. Water temperature has changed between dry and rainy periods and spatially it was influenced by the sampling timing. Nutrient concentrations are low and the main nitrogen compounds present were nitrate and ammonium, at the most impacted site, with highest values in the dry season. The highest variability was obtained for the total nitrogenvariability with higher concentrations at the dry season. Based on the trophic state index. The water of Cancã stream was classified as mesotrophic. The hydrographic microbasin has a non-regular shape, being slightly elongated and it has low vulnerability to floodings. The area of the catchment was found to be 3,071 Km2. Planktonic communities were composed by few organisms mainly occuring at the upper and middle stream streches, being most abundant at the first stretch. Clorophyceans and diatoms were the dominant groups among phytoplankton and the rotifers and cladocerans among the zooplankton. Cancã microbasin is subjected to a variety of agriculture and semi-intensive cattle enterprises that have changed major nutrient mass balances, contributing to the increase in nutrient loadings mainly via surface terrestrial runoff.