Rivers belong to the world’s most complex ecosystems but increasing demands for water are degrading rivers worldwide. The increase in human populations and activities has resulted in an intense and difficult conflict between the development of rivers as a natural resource and their function as living ecosystems. It is now widely recognized that a naturally variable flow regime is required to sustain freshwater ecosystems. Many countries that experience river degradation have started to implement environmental flows, i.e. the unallocated flow purposely preserved in a river. The objectives of this thesis are twofold. The first aim is to briefly describe the concept and science of environmental flows and the different methodologies for calculating environmental flows. This was done based on a literature review of the subject. The second aim is to present a case study calculating the environmental flow requirements. The case study was conducted through a field study in the Buzi River basin in Mozambique and the subsequent modeling of the environmental flow requirements. The literature study showed that not only the quantity of water is important; the timing and frequency of floods, droughts, low flows and high flows are very important as well. The literature study also showed that the advances in environmental flow science have been remarkable while the water policy and management has not been equally successful in implementing environmental flow standards. The calculation of environmental flow requirements was done with the Desktop Reserve Model developed in South Africa. The results indicated that to maintain the ecological status in the Buzi River at a largely natural condition (ecological category A) an average allocation of 57 % of mean annual runoff (MAR) is required. The present ecological status was determined in Revue River, which is one of the three major tributaries to Buzi River. To maintain the Revue River at its present ecological state requires an environmental flow between 23-37 % of MAR. The major environmental threats in Revue River are erosion and flow modification. The erosion is a consequence from artisanal gold mining, inadequate farming practices and deforestation. The flow alterations are caused by the large Chicamba Dam constructed for the generation of hydropower. One of the questions this thesis aimed to answer was if it was possible to set the present ecological state with a limited amount of data. This study showed that it could be possible but that the confidence level will be low. The relationships between ecological metrics and flow alterations must be investigated in detail for this region before environmental flow requirements can be successfully calculated and implemented. / Floder hör till jordens mest komplexa och känsliga ekosystem, men ett ökat tryck på våra vattenresurser har försämrat situationen för många av världens floder. Befolkningsökningen och den globala utvecklingen har resulterat i en intensiv och komplicerad konflikt mellan utnyttjandet av floder som en naturresurs och bevarandet av deras funktion som unika ekosystem. Det är nu allmänt accepterat att den naturliga flödesvariabiliteten behövs för att bevara våra sötvattenekosystem. Flera länder där försämringen av floder är ett faktum har börjat införa miljöanpassade flöden, det vill säga vatten som medvetet tilldelas flodens ekosystem. Det finns två syften med det här examensarbetet. Det första är att genom en litteraturstudie beskriva miljöanpassade flöden och de modeller som används för att beräkna detta flöde. Det andra målet är att göra en fallstudie och beräkna det miljöanpassade flödet och bestämma den ekologiska statusen för Buzi floden i Moçambique. Litteraturstudien visade att det inte bara är kvantiteten av vatten som är viktigt; tidpunkt och återkomsten av översvämning, torka, lågflöden och högflöden är mycket viktiga om man vill efterlikna det naturliga flödet. Litteraturstudien visade även att framstegen i kunskapen om miljöanpassade flöden har varit stora medan vattenlagstiftningens anpassning och införandet av miljöanpassade flöden har varit svag i flera avseenden. Modellerandet gjordes med den sydafrikanska Desktop Reserve Model. Resultaten från modellen visade att för att bibehålla den ekologiska statusen för Buzi floden i ett nära naturligt stadium (ekologisk klass A) krävs en tilldelning på 57% av medelårsavrinningen. Den nuvarande ekologiska statusen bestämdes i Revue floden, som är en av tre huvudfloder i Buzi avrinningsområdet. För att behålla Revue floden i sitt nuvarande tillstånd skulle kräva ett miljöanpassat flöde på mellan 23-37% av medelårsavrinningen. De största ekologiska hoten i Revue floden visade studien var erosion och flödesförändringar. Erosionen är en konsekvens av guldutgrävning, jordbruk med fel teknik, och skogs­­avverkning. Flödesförändringarna härrör från den stora vattenkraftsstationen Chicamba Dam. En av frågorna den här studien syftade till att besvara var om det är möjligt att bestämma den nuvarande ekologiska statusen med en begränsad tillgång till data. Studien visade att det är möjligt men att osäkerhetsnivån i resultatet kommer att vara stort. Studien visade även att modellen Desktop Reserve Model kan användas för snabba beräkningar av det miljöanpassade flödet, men att mer utförliga studier som till exempel Building Block Methodology måste genomföras innan resultatet med säkerhet kan verifieras. Relationen mellan ekologiska förändringar och flödesvariationer måste utredas i detalj för studieområdet innan de miljö­anpassade flödesbehoven kan bli implementerade med framgång.

Hydrologic Information Systems (HIS) have emerged as a means to organize, share, and synthesize water data. This work extends current HIS capabilities by providing additional capacity and flexibility for marine physical and chemical observations data and for freshwater and marine biological observations data. These goals are accomplished in two broad and disparate case studies – an HIS implementation for the oceanographic domain as applied to the offshore environment of the Chukchi Sea, a region of the Alaskan Arctic, and a separate HIS implementation for the aquatic biology and environmental flows domains as applied to Texas rivers. These case studies led to the development of a new four-dimensional data cube to accommodate biological observations data with axes of space, time, species, and trait, a new data model for biological observations, an expanded ontology and data dictionary for biological taxa and traits, and an expanded chain-of-custody approach for improved data source tracking. A large number of small studies across a wide range of disciplines comprise the “Long Tail” of science. This work builds upon the successes of the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) by applying HIS technologies to two new Long Tail disciplines: aquatic biology and oceanography. In this regard this research improves our understanding of how to deal with collections of biological data stored alongside sensor-based physical data. Based on the results of these case studies, a common framework for water information management for terrestrial and marine systems has emerged which consists of Hydrologic Information Systems for observations data, Geographic Information Systems for geographic data, and Digital Libraries for documents and other digital assets. It is envisioned that the next generation of HIS will be comprised of these three components and will thus actually be a Water Information System of Systems. / text

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La thèse constitue une juxtaposition de plusieurs contributions originales à lélaboration et lanalyse de modèles numériques capables de décrire une vaste gamme découlements à surface libre ainsi que les phénomènes de transport associés. Deux axes principaux sous-tendent les recherches entreprises. Il sagit, dune part, dune contribution à létude de modèles visant à reproduire adéquatement les interactions du fluide avec divers constituants transportés, tels que de lair entraîné, un polluant ou des sédiments. Cette phase du travail inclut également la caractérisation et la prédiction du comportement de lécoulement en présence dune topographie mobile ou érodable, y compris dans le cas dun barrage en remblai subissant une surverse. Dautre part, partant du constat quune modélisation fidèle des processus de transport, notamment hydrosédimentaires, passe inévitablement par un raffinement du calcul hydrodynamique proprement dit, une partie des travaux effectués dans le cadre de cette thèse est spécifiquement orientée vers un enrichissement de la connaissance des champs hydrodynamiques au sein du modèle.

The decline of floodplain vegetation along the Lower River Murray, South Australia, has evoked recommendations for ‘environmental flows’ to restore and maintain the health of the ecosystem. To assist managers to maximize benefits from environmental flows, this thesis considers the significance of water for germination and recruitment in key floodplain plant species. Three dominant species are considered, including two trees, river red gum (Eucalyptus camaldulensis) and black box (E. largiflorens), and an understorey shrub, tangled lignum (Muehlenbeckia florulenta). The soil seed bank was dominated by terrestrial annual native plants. Among 1400 seedlings, a single river red gum was found, and no black box or lignum, suggesting that these species do not contribute to the persistent soil seed bank and rely instead on aerial seed banks (serotiny). Sampling of the soil seed bank was continued to determine when seed fall might coincide with appropriate soil moisture conditions. Responses of the soil seed bank to varied water regimes were compared to determine requirements for seedling survival. The results indicated that species richness, rapidity of response and survival time were all promoted by sustained soil moisture. Stands of eucalypts in various states of health (from very stressed to very healthy) were monitored to identify seasonal patterns in bud crops, flowering, fresh leaves and volumes of seed released from the aerial seed bank. Distinct seasonal phenological patterns were apparent, and suggested alternating flowering among individual trees (biennial for red gum, bi-annual for black box), producing an annual peak in summer. Peak seed rain occurred in summer (December–March) in healthy trees for both red gum and black box, with light seed rain continuing throughout the year. Seed fall from stressed trees was much reduced. Stressed trees responded after a second watering event, with much more varied and extended annual seed fall patterns. Lignum showed a spring peak in flowering and seed production. There was a prolific response of flowering and seeding to rainfall, but few seedlings survived. Vigorous vegetative growth occurred in existing plants in response to rainfall and watering but no new cloned plants were found during the study. An investigation of chromosomes as a potential tool to appraise the balance between sexual and asexual reproduction in lignum proved inconclusive, although a previous report of octoploidy in lignum was confirmed. Seeds from all three species and lignum cuttings were tested for their responses to varied watering regimes, based on combinations of simulated rain and flood conditions. The optimal soil moisture for continued growth and survival in all seeds and cuttings was 10 25%, with moisture values <10% causing wilting and death. The results also suggested that red gum and black box seeds which germinate in water under flooded conditions need to be stranded onto moist soil at the water’s edge within 10 days, for the seedling to continue to grow. It was also concluded that germination on rain-moistened soil is a key supplementary mechanism for recruitment, particularly between irregular flood events. For greatest benefit, the timing of environmental flows should complement any seasonal rainfall and irregular flooding that may occur. Extension of suitable soil moisture conditions (10-25%) for as long as possible after >5 mm rainfall, or after over-bank flows, would increase chances for survival of seedlings. December is the most likely month for maximal benefit from watering in the Lower Murray Valley, for germination and recruitment, based on regional rainfall and flooding patterns. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1344528 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008