Water is a politically sensitive resource in the Near East and water stress is increasing. It is therefore vital that there is a strong understanding of past hydrological variability, so that the drivers of change can be better understood, and so that the links between the palaeoclimate and archaeological records in this key region in the development of human civilisation can be investigated. To be of most use, this requires high resolution records and a good understanding of palaeoseasonality. A sediment sequence spanning ~14,000 years has been retrieved from Nar Gölü, a lake in central Turkey. This thesis presents isotope data from carbonates, diatoms and bulk organic matter, in particular focussing on oxygen isotope (δ18O) analysis of carbonates (which detailed monitoring of the modern lake system shows to be a strong proxy for water balance) and comparing δ18Ocarbonate and δ18Odiatom data in order to examine palaeoseasonality. Improved techniques for the interpretation of carbonate isotope records of mixed mineralogies and the mass balance correction of diatom samples contaminated with minerogenic material are also proposed. Due to the high resolution δ18Ocarbonate data, it was possible to show that the rapidity of the Younger Dryas to Holocene transition at Nar Gölü was similar to that seen in North Atlantic records and that centennial scale arid events in the Holocene seem to occur at the time of cold periods in the North Atlantic. Taken together, this suggests a strong teleconnection between the two regions. However, the longer duration of the aridity peaks ~9,300 and ~8,200 years BP at Nar Gölü, compared with the more discrete cooling events at this time in the North Atlantic, suggest that there are additional controls on Near East hydroclimate. There is a multi-millennial scale trend of increasing δ18Ocarbonate values from the early to late Holocene. This ‘Mid Holocene Transition’ has previously been identified in the Near East, however here it is demonstrated that water balance and not a shift in the seasonality of precipitation was the primary cause. Finally, for the first time, the stability of Near East climate in the early Holocene is robustly demonstrated, suggesting that this could have been a key enabler of the development of agriculture at this time.

This thesis seeks to extend the work of Thornes and Scoging on hillslope processes in south east Spain by paying particular attention to the relative roles of surface and sub-surface water movement in gully head change on two contrasting soil types. Gully growth is a major agent of erosion in semi-arid environments, yet studies to date have assumed the dominance of surface wash, and only speculated on the role of subsurface water movement. The sampling design was based on the hillslope hydrological cycle and incorporates measures of precipitation, infiltration, and runoff and subsurface flow on catchment areas above gully heads. Additional data on vegetation and some soil properties were collected. The field work was undertaken on three occasions in the summer, autumn and spring of 1982/3 to examine seasonal variations. The analysis of surface flow was hindered by the drought which meant there were only 10 rain days in 1982, and only one storm occurred during the field sessions on 26 November 1982. Despite this several observations can be made. Wash volumes were twice as high on the marl on 26 November. Both lithologies are susceptible to relatively high erosion rates by surface wash although rates tend to be higher on the marl, and there is considerable variation on both lithologies. However for neither lithology is the amount of sediment transported sufficient to fill in the gullies in the medium term. The analysis of the subsurface hydrology shows that saturated conditions were not monitored anywhere, and maximum soil moisture values reached between 50--60% saturation on the marl and conglomerate soils. There are marked seasonal variations in soil moisture and most of the variation occurs in the upper horizons. Flux rates are negligble on the marl and dominantly in the vertical plane. On the conglomerate rates are much faster, and throughflow may well occur on occasions, and at rates exceeding e'apotranspiration. This will contribute to wetter conditions around and in gullies on the conglomerate.

Surface Flow Types (SFTs), distinctive patterns of disturbance on the surface of flowing water resulting from the interaction between flow and channel shape, were used to delimit meso-scale in-channel habitats in eight British lowland rivers to determine whether SFT mesohabitats were capable of being mapped, and were physically and biologically distinct. Five different SFTs - No Perceptible (NP), Smooth (SM), Rippled (RP), Unbroken wave (UW) and Upwelling (UP) - were investigated, a further three rare types (Chute, Broken wave and Confused) were mapped but not investigated further. Identification and mapping the extent of SFTs of was shown to be practical by estimating SFT mesohabitat extent onto large scale plans of the stream channel supported by differential Global Positioning Satellite technology. Mesohabitats were drawn as they existed, giving a large degree of variability in relation to channel shape and improving over several current rapid habitat mapping methods. The physical distinctiveness of five SFT mesohabitats was examined using data collected from 596 mesohabitats over a wide range of discharges. Mean column velocity and substrate grain size (dominant and sub-dominant) increased from NP, through SM and RP to UW. Velocity, substrate size and embeddedness of fine particles were significantly different (ANOVA and Pair-wise) between the five SFTs investigated. Substrate size was positively associated with increasing velocity, depth and embeddedness were negatively associated with velocity. PCA showed that substrate opposes embeddedness and velocity opposes depth. The degree of distinctiveness was diminished by data ranges which encompassed several SFTs. Macroinvertebrates were collected in 375 samples from 139 SFTs, using one-minute kick samples and identified to Biological Monitoring Working Party family level. ANOVA and Pair-wise analysis of Lotic-invertebrate Index for Flow Evaluation Velocity Group shows significant differences between 80% of SFT combinations with UP least distinct. Mean relative abundance and taxonomic richness increased from NP, through SM and RP to UW and were positively related to velocity. ANOVA showed significant differences between relative abundance and richness in SFTs, whilst Pair-wise analysis shows that adjacent SFTs, in relation to velocity, were less different than those further away. Thus NP is similar to SM and different to UW. Diversity and Equitability between SFTs were less distinct. Thirteen macroinvertebrate family groups were significantly associated (X2 Test) with particular Surface Flow Types, e.g. Ancylidae with UW; Chironomidae with NP. Biological distinctiveness was not established, although general trends were identified One mesohabitat – UP - is rare, being physically related to NP and SM in depth and substrate, and to SM and RP in velocity and embeddedness. It is biologically less distinct than the other four SFTs. The research shows that the extents of NP, SM, RP and UW mesohabitats in British lowland rivers are capable of being mapped. There are significant trends in their physical distinctiveness which are linked to increasing downstream velocity although is not strong. The macroinvertebrate relationship is weaker, with abundance and richness increasing with velocity.

Accurate characterisation of the hydraulic environment is a key step in describing hydromorphology at an ecologically relevant scale which has relevance to several aspects of river management, including monitoring river health, designing environmental flows and evaluating river rehabilitation measures. However, current hydraulic habitat quantification methods oversimplify the spatial heterogeneity of the hydraulic environment and do not explain or interpret the spatial arrangement of different habitat units sufficiently or define the dynamics of these shifting patterns. This research applied a novel numerical classification method and a landscape ecology framework to quantify the composition and configuration hydraulic patches in three UK lowland river reaches at five different flows. Five spatially coherent hydraulic patches, defined by the joint distribution of depth-velocity, were optimally delineated from hydraulic point data at each reach using the Gustafson-Kessel fuzzy clustering algorithm. Transitional zones between hydraulic patches occupied between 18- 30% and represent an application of the ecotone concept to the instream environment. Hydraulic patch diversity increased with discharge, peaking at high flow (Q38-Q22), suggesting that the provision of high flows is important for maximising hydraulic heterogeneity. The dominance of shallow, slow patches at low flow was gradually replaced by faster, deeper hydraulic patches at high flow illustrating the effect of discharge on the availability of different hydraulic patch types. The spatial arrangement of patches, quantified using a range of spatial metrics from the field of landscape ecology at two spatial scales (class and reachscape), was relatively invariant to changes in discharge suggesting that the configuration of the hydraulic patch mosaic is determined by channel morphology and remains stable between channel forming discharges. The majority of hydraulic patch types occurred in relatively fixed locations in the channel, moving relatively small distances as discharge increased, associated with the gradual expansion or contraction of patch area. The results suggest that sub-bankfull flow variations will primarily affect the composition rather than the configuration of hydraulic patches, however large fluctuations are likely to result in high rates of patch turnover (change in location), with potential implications for instream biota. The hydraulic patch/transition zone model of the hydraulic environment provides a new approach for exploring the link between physical and biological heterogeneity in the instream environment, including the role of instream ecotones. Whilst the application of numerical classification is currently limited by the large hydraulic data requirement, future advances in remote-sensing technology and hydrodynamic modelling are likely to widen its iii applicability at a range of spatial scales. The results highlight the need for further research on the ecological significance of hydraulic patches and transition zones and ecological sensitivity to changes in hydraulic patch configuration. Wider application of the landscape ecology approach to hydraulic habitat assessment in different reach types is recommended to improve understanding of the links between geomorphic and hydraulic diversity.

The use of catchment areas for the study of elemental mobilities is discussed with particular reference to two catchments in north-east Scotland. Underlying geology has considerable influence on their respective stream water compositions, although total annual solute output ultimately depends on the quantity of stream runoff. Tremendous fluctuations in stream water chemistry occur during storms which, it has been suggested, are due to the pathways taken by storm water through chemically contrasting soil horizons. Field sampling of this soil throughflow storm component and laboratory studies involving the leaching of undisturbed soil cores (taken at various depths down the profile) support this conclusion. Relationships between iron, aluminium and organic matter in stream water are discussed in detail. Full use of the available analytical facilities has been made with modifications to existing methods and development of new methods undertaken where necessary.

This study was concerned with the submerged bottom type of river intake, which consists, essentially, of a filter located in the river bed, through which water can be pumped. This type of intake has been used recently, for example, in salmon rivers, to minimise disruption of fish movement. The problem of assessing the change in bed shear stress over the intake was studied with a view to estimating the depth of the scour hole, which was known to be a feature associated with abstraction. The literature on local scour in alluvial channels was studied, several different types of scour being covered by the survey. Although most of the methods described were limited in application to a certain type of scour, some general principles were observed. In particular, it became clear that it was important to obtain an adequate description of the modification of the flow field giving rise to the scour. Several different turbulence models were assessed before a decision was made on the approach to be adopted to the problem. The more complex models were considered unsuitable, mainly because excessive attention to detail in the flow field would be unwarranted when other aspects of the problem, such as the suction force on the grains and the relationship between grain movement and boundary shear stress, were not known with sufficient accuracy. In addition, there was some uncertainty in the modifications to such models that would be required for their application to the intake problem. The extended law of the wall for suction flows was rejected because it is valid only for suction velocities up to about 1% of the external flow velocity, whereas the suction velocity in the intake flows studied ranged from 2% to 10% of the mean flume velocity. Solutions based on the mean flow momentum equation were studied, and a model was developed which was based on the hypothesis that the increase in shear stress at the bed was related directly to the momentum given up by the abstracted fluid at the bed. This model gave significantly improved predictions compared with a previous model, in respect of both the magnitude and pattern of shear stress distribution in the suction zone. It also had an advantage over the earlier model in that the results did not depend significantly on the assumption of a hydrostatic, or any other, pressure distribution in the main flow. Measurements of the modification of the velocity field associated with abstraction were made over a suction zone in a wind tunnel. The velocity profiles at a number of different points along the suction zone were measured using a hot-wire anemometer and these provided confirmation that the profiles assumed for the purposes of calculation gave an adequate description of the flow. Shear stress measurements over a model intake in a laboratory flume were made by observing the combinations of suction and flume flow which induced threshold conditions for sand grains placed on an impermeable disc in the suction zone, whose threshold shear stress in uniform flow was known. The measurements of shear stress using this method gave results which were between five and ten times lower than the predicted values, although they were comparable to estimates of shear stress based on the near-bottom velocities measured in the wind tunnel. It was deduced that the absence of suction at the disc itself was responsible for this large difference, since tests with dye showed that the disc did not interfere noticeably with the main flow. Measurements were also made of the bed profile over the model intake in the flume at various stages in the development of the scour hole, and the bed shear stress estimated from these measurements. These estimates showed a reasonable correlation with the predictions of the new mathematical model, but it was clear that there was a need for a better understanding, especially with regard to the interpretation of the experimental data. This study has provided a means of estimating the boundary shear stress associated with abstraction, and the resulting grain dislodgement rate and scour. These estimates are approximate in nature, but ways of obtaining improved predictions have been indicated, and these should provide a sound basis for an extension of this work to the study of three-dimensional scour which is important in the application of the results to intakes in practice.

A programme of field sampling was undertaken to quantify annual organic carbon fluxes at a range of sites on the River Dee and River Don in NE Scotland. The annual fluxes of both DOC and POC in the R. Dee and R. Don were found to increase cumulatively with distance down the river system. In headwater and tributary catchments of the R. Dee, annual DOC fluxes were positively related to the coverage of peat in the catchment area. This work as supplemented by a desk study in which organic carbon exports in 1993 were calculated for 85 large British rivers, using archive information. The resulting estimates, along with data on the soil carbon content of 17 river catchments were used to develop a predictive model of British riverine DOC fluxes. Calculated and predicted DOC fluxes and estimates of POC export based on suspended solids data, were combined to produce estimates of the annual British riverine organic carbon export during 1993. The 'non-storm' flux of DOC in British rivers in tidal waters during 1993 was estimated at 0.69 Mt +/- 0.28 Mt; the corresponding POC flux estimate was 0.2 Mt. A direct method for measuring dissolved CO2 in river and lake waters was developed. Preliminary studies of rivers in NE Scotland and lakes in Northern Wisconsin, USA, suggested that lakes may act as conduits for CO 2 transport, particularly in catchments containing substantial wetland. In conclusion, soil carbon content appears to be a useful integrative measurement for predicting annual DOC fluxes in British rivers. The establishment of a link between soil carbon stores and riverine fluxes, should help to improve future modelling of the carbon cycle. These findings suggests that rivers (and lakes) may regulate increases in soil carbon pools induced by climate change.

The River Don discharges into the North Sea by way of a small estuary on the northern outskirts of the city of Aberdeen. This thesis aims to establish the patterns of mixing of river and seawater within the estuary and its associated coastal waters, and to interpret those factors that affect these patterns. Fieldwork consisted mainly of boat borne surveys of salinity, temperature and currents. This programme was augmented with air based visual observations, and a photogrammetric survey of surface water movement using fluorescent dyes. River flow data was acquired from the North East River Purification Board, and wind records from Total Oil Marine Ltd., Altens. Estuarine mouth configuration was monitored via bimonthly tacheometric surveys. The estuary was found to be highly stratified under mean conditions, a distinct saltwedge penetrating upstream beneath seaward flowing freshwater during the flooding tide. The extent of this saline intrusion depends upon the freshwater head, as represented by river flow; and the tidal head, as represented by the height of high water. During the ebbing tide the saline waters are completely flushed from the estuary, except where retained within the depths of 'potholes'. Under particularly high river flows saline penetration is prevented at all stages of the tide. Mixing during the flooding tide was by entrainment of freshwater down into the advancing salt wedge. However, only during the ebbing tide does a high level of mixing occur, as a result of increased turbulent diffusion, causing a rise in surface salinity. Under most conditions, therefore, fresh or brackish water spreads seawards from the estuary mouth, forming a thin, highly buoyant plume. As a result of buoyant spread and inertia induced turbulence, mixing of these waters is intense in the zone immediately seaward of the mouth. However, mixing is not complete and the waters form a thin surface layer which may preserve its identity for several kilometres beyond this initial zone. The direction of spread of this buoyant discharge is chiefly determined by the tidal stream, although initially by the geometry of the estuary mouth. During the ebbing tide the plume forms to the north of the mouth, and during the flood, to the south. Wind and wave induced currents may enhance or restrict the spread of these surface waters. Storm wave activity, causing mixing of estuarine discharge as soon as it leaves the outlet, precludes the formation of a buoyant plume. Restricted estuarine discharge during the flood tide, and enhanced discharge during the ebb, result in the ebb plume being a considerably more extensive feature. The plume was often demarcated by a sharp thermohaline front marked by a distinct colour change. The front was a zone of strong surface convergence, and, consequently, was often demarcated by a collection of foam and floating debris.

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