Effects of Linking a Soil‐Water‐Balance Model with a Groundwater‐Flow Model

A previously published regional groundwater‐flow model in north‐central Nebraska was sequentially linked with the recently developed soil‐water‐balance (SWB) model to analyze effects to groundwater‐flow model parameters and calibration results. The linked models provided a more detailed spatial and temporal distribution of simulated recharge based on hydrologic processes, improvement of simulated groundwater‐level changes and base flows at specific sites in agricultural areas, and a physically based assessment of the relative magnitude of recharge for grassland, nonirrigated cropland, and irrigated cropland areas. Root‐mean‐squared (RMS) differences between the simulated and estimated or measured target values for the previously published model and linked models were relatively similar and did not improve for all types of calibration targets. However, without any adjustment to the SWB‐generated recharge, the RMS difference between simulated and estimated base‐flow target values for the groundwater‐flow model was slightly smaller than for the previously published model, possibly indicating that the volume of recharge simulated by the SWB code was closer to actual hydrogeologic conditions than the previously published model provided. Groundwater‐level and base‐flow hydrographs showed that temporal patterns of simulated groundwater levels and base flows were more accurate for the linked models than for the previously published model at several sites, particularly in agricultural areas.     

Intertidal zone of Delaware Inlet,Nelson, New Zealand

Abstract

A study was made of Delaware Inlet (41° 10'S, 173° 26’ E), Nelson, New Zealand, during February—April 1976. The catchment contains sparse animal and human populations, and supplies unpolluted influent waters.

Over 90% of the inlet was intertidal, with surfaces of predominantly sand interspersed with mud, gravel, cobbles, and shell. Less than 10% of the sediments were colonised by macroscopic vegetation, principally Juncus spp. with Salicornia australis, Zostera muelleri, Viva lactuca and Enteromorpha spp. Two microscopic organisms (Euglena obtusa and Oscillatoria ornata) were studied. Dense aggregations of molluscs, particularly Amphibola crenata (mud snail) and Chione stutchburyi (cockle) were present in specific areas.

Salinity of the water fluctuated widely from <4‰ at the river mouth to 35.0‰ in the main channel at high tide. Nitrogen levels (N0₂‐N, NO₃‐N, NH₄‐N, Kjeldahl‐N) were determined on influent and waters of the inlet. For the main channel, levels of NO₃‐N, NH₄‐N and Kjeldahl‐N tended to be substantially higher around low water than at high tide; respective maxima and minima were 0.016 and 0.001 g.m^?3, 0.050 and 0.001 g.m^?3, and 0.35 and 0.10 g.m^?3. For water from river and streamlets, average levels of nitrogen components were similar to those for the main channel at low tide.     

Winter oceanographic observations in some New Zealand fiords

The winter oceanography of four New Zealand fiords is discussed using data obtained from July 1983, and comparisons are made with data collected on previous summers. Surface waters were more saline in winter than in summer and were everywhere cooler than the underlying water. Deep water renewal in the fiord basins was re‐examined using all available data. For Milford Sound and the other deep silled fiords renewal appears to be related to the arrival of dense water at sill depth offshore by an as yet unknown advective or meteorologically forced process. In the more isolated Long Sound, Preservation Inlet, deep water renewal requires the subtle interplay of tidal flows and mixing processes over the shallow double sill. Complete renewal of Long Sound bottom water appears to be a slow process.     

Two‐dimensional model of diffusion processes around a river mouth

The steady state diffusion equation is solved for two‐dimensional flow around a point source along an infinite straight boundary. Solutions obtained are related to the observed distribution of temperature and salinity around the mouth of the Buller River, South Island, New Zealand.     

Rates of zinc and trace metal release from dissolving sphalerite at pH 2.0–4.0

High-Fe and low-Fe sphalerite samples were reacted under controlled pH conditions to determine nonoxidative rates of release of Zn and trace metals from the solid-phase. The release (solubilization) of trace metals from dissolving sphalerite to the aqueous phase can be characterized by a kinetic distribution coefficient, (D_tr), which is defined as [(R_tr/X(tr)_Sph)/(R_Zn/X(Zn)_Sph)], where R is the trace metal or Zn release rate, and X is the mole fraction of the trace metal or Zn in sphalerite. This coefficient describes the relationship of the sphalerite dissolution rate to the trace metal mole fraction in the solid and its aqueous concentration. The distribution was used to determine some controls on metal release during the dissolution of sphalerite. Departures from the ideal D_tr of 1.0 suggest that some trace metals may be released via different pathways or that other processes (e.g., adsorption, solubility of trace minerals such as galena) affect the observed concentration of metals.     

An example of fingerprint detection of greenhouse climate change

As an example of the technique of fingerprint detection of greenhouse climate change, a multivariate signal or fingerprint of the enhanced greenhouse effect is defined using the zonal mean atmospheric temperature change as a function of height and latitude between equilibrium climate model simulations with control and doubled CO₂ concentrations. This signal is compared with observed atmospheric temperature variations over the period 1963 to 1988 from radiosonde-based global analyses. There is a significant increase of this greenhouse signal in the observational data over this period.These results must be treated with caution. Upper air data are available for a short period only, possibly too short to be able to resolve any real greenhouse climate change. The greenhouse fingerprint used in this study may not be unique to the enhanced greenhouse effect and may be due to other forcing mechanisms. However, it is shown that the patterns of atmospheric temperature change associated with uniform global increases of sea surface temperature, with El NinoSouthern Oscillation events and with decreases of stratospheric ozone concentrations individually are different from the greenhouse fingerprint used here.     

Exhalative metasediments – clues to the real nature of regional metamorphic processes?

Summary Regional metamorphic petrogenetic theory is currently dominated by the hypothesis that the principal grade indicator silicates and their related minerals arise by a variety of chemical reactions. It is postulated that, with rise (or fall) in regional crustal temperature and pressure, original materials become destabilized, break down, and are dissolved in the intergranular metamorphic fluid. The resulting ions then diffuse within, and are transported by, this fluid, in due course reacting with each other to form new minerals in equilibrium with each other and the associated fluid under the new conditions and in accordance with the Phase Rule. A second mechanism, widely accepted for such as metamorphic oxide, carbonate, sulphate and sulphide minerals, but not for the principal metamorphic silicates, is that the latter form largely by in situ solid:solid transformation plus or minus SiO₂ plus or minus H₂O, rather than by the serial process indicated above. It is now proposed that a test of the reaction theory is whether or not chemical equilibrium has been established on a fine (grain) scale in materials metamorphosed to high grades. On the basis of some simple – but very precise – electron microprobe measurements on some high grade, but still finely bedded, exhalative metasedimentary rocks, it appears to fail the test.