Automated riverine landscape characterization: GIS-based tools for watershed-scale research, assessment, and management

River systems consist of hydrogeomorphic patches (HPs) that emerge at multiple spatiotemporal scales. Functional process zones (FPZs) are HPs that exist at the river valley scale and are important strata for framing whole-watershed research questions and management plans. Hierarchical classification procedures aid in HP identification by grouping sections of river based on their hydrogeomorphic character; however, collecting data required for such procedures with field-based methods is often impractical. We developed a set of GIS-based tools that facilitate rapid, low cost riverine landscape characterization and FPZ classification. Our tools, termed RESonate, consist of a custom toolbox designed for ESRI ArcGIS®. RESonate automatically extracts 13 hydrogeomorphic variables from readily available geospatial datasets and datasets derived from modeling procedures. An advanced 2D flood model, FLDPLN, designed for MATLAB® is used to determine valley morphology by systematically flooding river networks. When used in conjunction with other modeling procedures, RESonate and FLDPLN can assess the character of large river networks quickly and at very low costs. Here we describe tool and model functions in addition to their benefits, limitations, and applications.     

Characterizing sources of nitrate leaching from an irrigated dairy farm in Merced County, California

Dairy farms comprise a complex landscape of groundwater pollution sources. The objective of our work is to develop a method to quantify nitrate leaching to shallow groundwater from different management units at dairy farms. Total nitrate loads are determined by the sequential calibration of a sub-regional scale and a farm-scale three-dimensional groundwater flow and transport model using observations at different spatial scales. These observations include local measurements of groundwater heads and nitrate concentrations in an extensive monitoring well network, providing data at a scale of a few meters and measurements of discharge rates and nitrate concentrations in a tile-drain network, providing data integrated across multiple farms. The various measurement scales are different from the spatial scales of the calibration parameters, which are the recharge and nitrogen leaching rates from individual management units. The calibration procedure offers a conceptual framework for using field measurements at different spatial scales to estimate recharge N concentrations at the management unit scale. It provides a map of spatially varying dairy farming impact on groundwater nitrogen. The method is applied to a dairy farm located in a relatively vulnerable hydrogeologic region in California. Potential sources within the dairy farm are divided into three categories, representing different manure management units: animal exercise yards and feeding areas (corrals), liquid manure holding ponds, and manure irrigated forage fields. Estimated average nitrogen leaching is 872 kg/ha/year, 807 kg/ha/year and 486 kg/ha/year for corrals, ponds and fields respectively. Results are applied to evaluate the accuracy of nitrogen mass balances often used by regulatory agencies to assess groundwater impacts. Calibrated leaching rates compare favorably to field and farm scale nitrogen mass balances. These data and interpretations provide a basis for developing improved management strategies.     

Limitations of an optimum sustainable population or potential biological removal approach for conserving marine mammals: Pacific walrus case study

Decision rules are the agreed-upon points at which specific management interventions are initiated. For marine mammal management under the U.S. Marine Mammal Protection Act (MMPA), decision rules are usually based on either a numeric population or biological-removal approach. However, for walrus and other ice-associated pinnipeds, the inability to reliably assess population numbers or biological removals highlights a significant gap in the MMPA, particularly when the Arctic environment is rapidly changing. We describe the MMPA's ecosystem-based management goals, and why managers have bypassed these goals in favor of an approach that depends upon numerical population assessment. We then revisit the statute's primary goals in light of current knowledge about the Pacific walrus ecosystem and new developments in environmental governance. We argue that to monitor and respond to changes in the walrus ecosystem, decision rules should be based on scientific criteria that depend less on the currently-impractical goal of accurately enumerating population size and trends, or removals from that population. Rather, managers should base decisions on ecological needs and observed ecological changes. To implement this approach would require an amendment to the MMPA that supports filling the gap in management with achievable decision rules. Alternatively, walrus and other ice-associated pinnipeds will remain largely unmanaged during a period of profound environmental change.     

Long-term depletion of calcium and other nutrients in eastern US forests

Both harvest removal and leaching losses can deplete nutrient capital in forests, but their combined long-term effects have not been assessed previously. We estimated changes in total soil and biomass N, Ca, K, Mg, and P over 120 years from published data for a spruce-fir site in Maine, two northern hardwood sites in New Hampshire, central hardwood sites in Connecticut and Tennessee, and a loblolly pine site in Tennessee. For N, atmospheric inputs counterbalance the outputs, and there is little long-term change on most sites. For K, Mg, and P, the total pool may decrease by 2%–10% in 120 years depending on site and harvest intensity. For Ca, net leaching loss is 4–16 kg/ha/yr in mature forests, and whole-tree harvest removes 200–1100 kg/ha. Such leaching loss and harvest removal could reduce total soil and biomass Ca by 20%–60% in only 120 years. We estimated unmeasured Ca inputs from rock breakdown, root-zone deepening, and dry deposition; these should not be expected to make up the Ca deficit. Acid precipitation may be the cause of current high leaching of Ca. Although Ca deficiency does not generally occur now in acid forest soils, it seems likely if anthropogenic leaching and intensive harvest removal continue.     

Comparative analysis of air pollution emissions by electric utilities: Public policy implications

One of the objectives of US environmental regulations was to reduce industrial air pollution emissions, especially from the electric utility industry, the major industrial air polluter. In this study, a comparative analysis of air pollution emissions from fossil-fuel-burning electric utility plants is conducted. The analysis focuses on a 12-yr period from 1975 to 1987 for three air pollutants: particulates, surfur dioxide, and nitrogen oxides. The results indicate that particulate emissions have been significantly reduced but that sulfur dioxide and nitrogen oxides are still major problems for a number of plants. Furthermore, the disparity in the performance by plants indicates that by using current technology, the industry as a whole could greatly reduce these emissions. These results have policy implication for future environmental legislation.     

Urban growth management in Jeddah

The towns and cities of Saudi Arabia have been subjected to sustained growth pressures since the transformation of the country's economy following the discovery of oil in the Eastern Province of the Kingdom. The rapid growth which has been experienced has created major problems for the central and local government agencies responsible for planning and managing urban growth. The experience of Jeddah, one of the major cities in Saudi Arabia, is described and the problems of planning and managing its growth are analysed. Weaknesses relating to the structure of the planning system are identified, as are major difficulties in relation to the quality and quantity of professional staff. Recent attempts to improve the operation of the planning system are described and evaluated.     

Morphologie effects of channelization: the case of the Neebing-McIntyre floodway,Thunder Bay,Ontario, Canada

The Neebing-McIntyre floodway in Thunder Bay, Ontario, Canada, has been constructed with a relatively straight and uniform trapezoidal channel, compared with the prechannelized sinuous reaches of the Neebing and the McIntyre rivers. The flow regime of the floodway also contrasts significantly with the prechannelized regime, because of the combination of discharges from these rivers into a new channel and the regulation of flows by a diversion structure. The maximum channel capacity of the floodway is about 284 m³ s^–1 (175-year regional flood), compared with about 40 m³ s^–1 and 60 m³ s^–1, respectively, for the Neebing and the McIntyre. According to regime theories, the construction of a straight and trapezoidal channel has upset the equilibrium of the stream system and therefore should lead to some accelerated erosion and sedimentation processes in the new channel immediately after construction. Erosion potential is particularly high during higher discharge events, when flow velocities are expected to be greater than the prechannelized velocities of the Neebing and the McIntyre. The overall sediment yield of the watershed is low (71t km^–2 yr^–1), compared with other documented watersheds of North America, but the rates of deposition in the floodway are relatively high, mainly due to the backwater effect of Lake Superior. Unless maintained by constant channel work, the floodway will tend to fill up with sediment, until a postconstructional equilibrium is reestablished.