Orifice Plates to Control the Capacity of Terrace Intake Risers

This is the published version. Copyright 1989 American Society of Agricultural and Biological EngineersThe flow in the conduit from upslope terraces JL must be controlled so that there is no excess hydraulic head under a lower terrace, causing water to flow up through the riser, which could result in the terrace overtopping (Schwab et al., 1981). Based upon economic considerations, an orifice plate is used to minimize the conduit size. This experimental study was conducted to evaluate the hydraulic characteristics of different combinations of riser-orifice plate openings. One open-top and two round-hole terrace intake risers were tested under laboratory conditions using three diameters of orifice plates. The drop-inlet spillway model was used to describe discharge characteristics. Equations and curves were constructed for the head-discharge relationships of various riser-orifice plate combinations

Scaling of Reference Reach for Desired Bankfull Discharge

The reference reach method is commonly used for natural stream design. In the reference reach approach, a stable reach is selected to serve as the design template for a design reach. The planform and profile of this reference reach must be scaled to fit the design site. Currently, the leading method for scaling uses a simple ratio of cross-sectional areas. This paper presents a simple method that employs hydraulic scaling to size the design reach to accommodate the desired bankfull flow. The method introduced in this paper is easy to use, does not require additional survey data, and should lead to more robust channel design

Magnetic fabric in ilmeniterich norites of the Bjerkreimer-Sokndal Layered Intrusion, Norway

The Bjerkreim-Sokndal (BKS) is a layered intrusion, located in the Mid- Proterozoic Egersund anorthosite-norite province within the Sveconorwegian province of the Baltic Shield, south Norway. The layered intrusion formed by influxes of more primitive magma into more evolved magma to produce six Megacyclic units (MCU), each of which can be divided into up to six subunits. From bottom to top in each megacycle the rocks consist of early plagioclase-rich norites, intermediate hemo-ilmenite-rich norites and later magnetite-rich norites. Aeromagnetic maps over the intrusion show large negative and positive anomalies. A negative anomaly with amplitude to - 13000 nT at 60m above ground is associated with hemo-ilmenite-rich norite layer MCU Ive. This layer IVe contains plagioclase, orthopyroxene, hemoilmenite, magnetite, and minor clinopyroxene, biotite, apatite and sulfides. Multi-domain (MD) magnetite makes up 2–3% of the rock. The negative magnetic anomaly associated with MCU IVe reaches its most negative value on the east limb of the Bjerkreim Lobe near Heskestad. The anomaly at Heskestad is part of a longer negative anomaly, which follows MCU IVe for more than 20 km around a large syncline. The average NRM intensity decreases from 25AM−1 along the east fold limb to 10AM−1 towards the hinge area to 7AM−1 at the hinge. The BKS has a penetrative deformation fabric within the syncline with the weakest deformation found in the hinge area and the strongest on the east limb. Electron backscatter diffraction (EBSD) was used to determine the lattice-preferred orientation (LPO) of orthopyroxene and ilmenite. The (100)-planes of the orthopyroxenes are found to lie parallel to a foliation in the rock, which is subparallel to the cumulate layering. Orthopyroxene c-axes form the steep lineation within the foliation plane. The anisotropy of magnetic susceptibility (AMS) was measured for samples that were taken at five locations from the eastern limb to the hinge area of the syncline to investigate if the change in NRM intensity could be related to magnetic fabric.conferenc

Crystallographic—magnetic correlations in single-crystal haemo-ilmenite: new evidence for lamellar magnetism

17 single crystals were identified by electron backscatter diffraction (EBSD) and isolated from coarse massive haemo-ilmenite ore from South Rogaland, Norway. These were studied using the EBSD results, natural remanent magnetization (NRM), and anisotropy of magnetic susceptibility (AMS), to gain a better understanding of angular relationships between crystallographic axes and magnetic properties of haemo-ilmenite in relation to lamellar magnetism. Electron microprobe analyses gave the following average end-member compositions for ilmenite host: 21.1 per cent MgTiO3, 73.7 FeTiO3, 0.5 MnTiO3, 4.3 Fe2O3, 0.2 Cr2O3 and 0.3 V2O3; and for the coarsest (∼3 μm) haematite exsolution lamellae: 3.5 MgTiO3, 22.4 FeTiO3, 71.4 Fe2O3, 1.6 Cr2O3, 1.0 V2O3 and 0.1 Al2O3, making this sample the most Mg- and Cr-rich haemo-ilmenite studied in the province, but with similar element fractionations between the coexisting phases. TEM work on similar material suggests the presence of much thinner exsolution down to 1-2 nm. The EBSD, NRM and AMS results from 12 out of 17 crystals indicate a good agreement between the orientation of crystallographic axes, NRM direction and principal axes of the magnetic susceptibility ellipsoid, with the NRM located in the (0001) basal plane [NRM ∧ (0001) < 6.5°] and the crystallographic c axis quasi-parallel to the minimum axis of the susceptibility ellipsoid [c∧ k3 < 13.5°]. In addition, in 10 of these 12 crystals, the remanent magnetization vector is parallel or nearly parallel to the positive direction of a crystallographic a axis [NRM ∧a < 20°], hence parallel to a principal magnetic moment direction in haematite as determined by Besser, and not parallel to the spin-canted direction of end-member haematite. This is consistent with a basic property of lamellar magnetism, where the magnetic moment is parallel to the principal moments (sublattice magnetization directions) in haematite. Relationships in three additional crystals with NRM ∧a= 22°-33°, only two with good agreement, can be interpreted as consistent with having a magnetic vector quasi-parallel to the spin-canted direction of haematit

Management Effects on Greenhouse Gas Dynamics in Fen Ditches

Globally, large areas of peatland have been drained through the digging of ditches, generally to increase agricultural production. By lowering the water table it is often assumed that drainage reduces landscape-scale emissions of methane (CH4) into the atmosphere to negligible levels. However, drainage ditches themselves are known to be sources of CH4 and other greenhouse gases (GHGs), but emissions data are scarce, particularly for carbon dioxide (CO2) and nitrous oxide (N2O), and show high spatial and temporal variability. Here, we report dissolved GHGs and diffusive fluxes of CH4 and CO2 from ditches at three UK lowland fens under different management; semi-natural fen, cropland, and cropland restored to low-intensity grassland. Ditches at all three fens emitted GHGs to the atmosphere, but both fluxes and dissolved GHGs showed extensive variation both seasonally and within-site. CH4 fluxes were particularly large, with medians peaking at all three sites in August at 120-230 mg m-2 d-1. Significant between site differences were detected between the cropland and the other two sites for CO2 flux and all three dissolved GHGs, suggested that intensive agriculture has major effects on ditch biogeochemistry. Multiple regression models using environmental and water chemistry data were able to explain 29-59% of observed variation in dissolved GHGs. Annual CH4 fluxes from the ditches were 37.8, 18.3 and 27.2 g CH4 m-2 yr-1 for the semi-natural, grassland and cropland, and annual CO2 fluxes were similar (1100 to 1440 g CO2 m-2 yr-1) among sites. We suggest that fen ditches are important contributors to landscape-scale GHG emissions, particularly for CH4. Ditch emissions should be included in GHG budgets of human modified fens, particularly where drainage has removed the original terrestrial CH4 source, e.g. agricultural peatlands