No abstract

The disappearance of imazethapyr [(±)‐2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazole‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid] from soil solution was investigated to evaluate the transport of imazethapyr in undisturbed soil columns. Soil treated with imazethapyr was incubated for 0.15, 1, 2, 4, 8, and 16 d, at which times soil solution was obtained by vacuum displacement. Bromide and imazethapyr were then applied to the surface of undisturbed soil columns followed by application of deionized water at approximately 3 cm d−1. The removal of imazethapyr from solution (i.e., sorption) exhibited biphasic kinetics and was well described (R2 = 0.99) by two simultaneous first‐order reactions. The initial reaction was essentially instantaneous and the secondary reaction was time dependent. The classical convective‐dispersive (CD) equation was used to describe solute transport through undisturbed soil columns. Bromide and imazethapyr breakthrough curves (BTCs) were displaced to the left of one pore volume and showed considerable tailing, with imazethapyr BTCs retarded in relation to Br‐. This was indicative of preferential solute mobility in the soil. Imazethapyr BTCs were similar to model simulations using transport parameters determined from Br‐ BTCs, kinetic parameters from the imazethapyr solution concentration decay curves, and retardation factors calculated from the distribution coefficient at the 1‐d incubation time. Model simulations using retardation factors from later times predicted increasingly delayed imazethapyr breakthrough with lower peak concentrations than measured. Preferential flow paths apparently reduced attenuation of imazethapyr as predicted from equilibrium adsorption measurements.

The determination of manure loading rates for crop production is complicated by the temporal variability in manure nutrient concentrations and the difficulty in obtaining representative samples on which to base application rates. The variation in nutrient concentrations in liquid swine manure obtained from an agitated anaerobic lagoon was examined during application to experimental plots. Grab samples were collected from a lagoon approximately two to four weeks prior to application and analyzed for nitrogen (N), phosphorus (P), and potassium (K). Based on the preliminary P analyses, swine manure application rates were computed. Manure from the lagoon was surface-applied to corn plots to provide P rates of 15, 30, and 60 kg P/ha. During application, each tankload of manure was sampled to determine P rates for each plot. The solids content of each manure load was highly variable as were the total concentrations of manure N and P. Potassium content of the manure was also related to the solids content, although not to the same extent as N and P. Manure application resulted in P rates of 17, 32, and 49 kg P/ha in 1992, while the 1993 rates were 5, 11, and 22 kg P/ha. The inability to achieve target P rates resulted from changes in nutrient concentrations between the time of initial manure chemical characterization and manure application. Variability in the solids content was identified as the major factor influencing nutrient concentrations among spreader tankloads.

Abstract. Flood-protection levees have been built along rivers and coastlines globally. Current datasets, however, are generally confined to territorial boundaries (national datasets) and are not always easily accessible, posing limitations for hydrologic models and assessments of flood hazard. Here we present our work to develop a single, open-source global river delta levee data environment (openDELvE) which aims to bridge a data deficiency by collecting and standardising global flood-protection levee data for river deltas. In openDELvE we have aggregated data from national databases as well as data stored in reports, maps, and satellite imagery. The database identifies the river delta land areas that the levees have been designed to protect, and where additional data is available, we record the extent and design specifications of the levees themselves (e.g., levee height, crest width, construction material) in a harmonised format. openDELvE currently contains 5,089 km of levees on deltas, and 44,733.505 km2 of leveed area in 1,601 polygons. For the 152 deltas included in openDELvE, on average 19 % of their habitable land area is confined by verifiable flood-protection levees. Globally, we estimate that between 5 % and 54 % of all delta land is confined by flood-protection levees. The data is aligned to the recent standards of Findability, Accessibility, Interoperability and Reuse of scientific data (FAIR) and is open-source. openDELvE is made public on an interactive platform (www.opendelve.eu), which includes a community-driven revision tool to encourage inclusion of new levee data and continuous improvement and refinement of open-source levee data.

Abstract. Flood-protection levees have been built along rivers and coastlines globally. Current datasets, however, are generally confined to territorial boundaries (national datasets) and are not always easily accessible, posing limitations for hydrologic models and assessments of flood hazard. Here, we bridge this knowledge gap by collecting and standardizing global flood-protection levee data for river deltas into the open-source global river delta levee data environment, openDELvE. In openDELvE, we aggregate levee data from national databases, reports, maps, and satellite imagery. The database identifies the river delta land areas that the levees have been designed to protect. Where data are available, we record the extent and design specifications of the levees themselves (e.g., levee height, crest width, construction material) in a harmonized format. The 1657 polygons of openDELvE contain 19 248 km of levees and 44 733.505 km2 of leveed area. For the 153 deltas included in openDELvE, 17 % of the land area is confined by flood-protection levees. Around 26 % of delta population lives within the 17 % of delta area that is protected, making leveed areas densely populated. openDELvE data can help improve flood exposure assessments, many of which currently do not account for flood-protection levees. We find that current flood hazard assessments that do not include levees may exaggerate the delta flood exposure by 33 % on average, but up to 100 % for some deltas. The openDELvE is made public on an interactive platform (https://www.opendelve.eu/, 1 October 2022), which includes a community-driven revision tool to encourage inclusion of new levee data and continuous improvement and refinement of open-source levee data.