RUNOFF AND WATER QUALITY FROM THREE SOIL LANDFORM UNITS ON MANCOS SHALE1

ABSTRACT: Relative yields of water, sediment, and salt (as indexed by electrical conductivity) were determined using simulated rainfall plots on three soil landform units on Mancos shale in the Price River Basin, Utah. Final infiltration rates on residual shale derived soils were between 0.13 and 0.50 cm/hr. No runoff was generated on cracked soils derived from aeolian deposits. Suspended sediment concentrations and elehcal conductivities were 180 and 68 times greater, respectively, for a steep dissected Mancos shale upland than for a low relief shale pediment and recent alluvial surface. Riling accounted for approximately 80 percent of the sediment produced on the steep, dissected shale surface. Channel scow and soil creep also produced measurable mounts of sediment. A survey of sediment basins in steep, dissected shale up lands indicated that an average of 1.25 Mg/ha/year of sediment is produced by that landform unit Carefully designed and located basin plugs can be used effectively to trap sediment, water, and salt from dissected shale uplands.     

Diversion of water flow from a floodplain wetland stream: an analysis of geomorphological setting and hydrological and ecological consequences

Diversion of water has been ongoing in the Mkuze Wetland for several decades. Two canals form the focus of this study; the Mpempe-Demazane Canal and the Tshanetshe Canal. The former involved an ambitious excavation over a distance of 13.5 km in the lower part of the wetland, while the latter was a minor excavation over a distance of approximately 100 m in the upper part of the wetland. Although ambitious and costly, the Mpempe-Demazane Canal resulted in little downward or headward erosion, and there was minor diversion of flow. However, the minor excavation of the Tshanetshe Canal resulted in erosion downstream of the excavation (the Tshanetshe Stream), downward and lateral erosion of the excavated section, and headward erosion that has propagated almost 4 km upstream along the Mkuze River. Most of the flow of the Mkuze River has been captured by the Tshanetshe Canal and Stream. The impact of canalisation on floodplain wetlands is thus more dependent on the location than the scale of activity. The avulsion of the Mkuze River into the Tshanetshe Canal and Stream is due to a large difference in elevation between the Mkuze River and floodplain into which it was diverted, and the fact that in this region the river typically has high discharges. This avulsion may have been inevitable as a result of natural processes of sedimentation. In contrast, the difference in elevation between the Mkuze River and the basin into which it was diverted via the Mpempe Canal was small as is discharge of the Mkuze River in this part of the wetland. Thus, the diversion was unsuccessful. The presence of hippos that create hydraulically efficient pathways that are oriented parallel to the regional hydraulic slope, may accelerate avulsion in large African wetlands. Overall, it is argued that the environmental consequences of excavation need to be viewed against the background that wetlands are dynamic features within the landscape.     

SEDIMENT TRAPPING WITHIN FORESTRY STREAMSIDE MANAGEMENT ZONES: GEORGIA PIEDMONT,USA1

ABSTRACT: The effectiveness of streamside management zones (SMZs) was assessed for reducing sediment transport from concentrated overland flow draining two Georgia Piedmont clearcuts that had undergone mechanical and chemical site preparation and planting. Silt fences were used to trap sediment transport from zero‐order ephemeral swales at the edge of and within SMZs. Four control swales and nine treatment swales were studied. A double mass curve approach was used to graphically compare sediment accumulation rates at the edge of SMZs to accumulation rates within the SMZs at a distance consistent with current recommendations for SMZ width in Georgia. SMZ efficiencies for trapping sediment transported by concentrated flow ranged from 71 to 99 percent. No statistical model was found to explain how SMZ efficiencies varied with SMZ and contributing area characteristics. Measured sediment accumulations at the SMZ boundary were compared to Revised Universal Soil Loss Equation (RUSLE) predictions of up‐ slope erosion, and a delivery ratio of 0.25 was calculated. SMZs had a quantifiable and substantial ameliorating effect on sediment transport from concentrated overland flow on the clearcut study sites.     

EARLY MORNING CANOPY TEMPERATURES FOR EVALUATING WATER STRESS IN A WHEAT CROP1

ABSTRACT: Several crop water stress indices were examined to determine their potential for use from a space-based system. These indices were compared using data collected over a wheat crop grown under arid environmental conditions. Indices that required concurrent ground-based measurements were less adaptable than the simple difference between canopy temperatures of a field with unknown stress conditions and a similar crop known to be unstressed. The results indicate that it would be feasible to develop space-based crop water stress techniques that would be useful for scheduling irrigations.     

Threats to beach resources and park boundaries caused by shoreline migration in an urban estuarine park

An evaluation of coastal processes, shoreline erosion, and shore management options for Conference House Park, New York, USA, reveals the problems associated with lack of congruence between jurisdictional boundaries and boundaries required for maintenance of beaches and shorefront park land. Rates of shoreline change are high despite low wave energies because bay beaches contain small amounts of sand. The park is so narrow in places that the shoreline will soon move out of park boundaries. This condition will eliminate natural beach resources, restrict access, and create political and administrative problems. Management strategies include revetment construction, beach nourishment, and acquisition of additional land. Obtaining the maximum length of shorefront to create a park may be less cost effective in maintaining natural beach resources than obtaining a shorter frontage and more compact shape that allows for shoreline movement. The problems of managing eroding shorelines in urban estuaries are acute because space is lacking, the cost of land is high, and the critical nature of shoreline erosion is disguised by low wave energies and lack of daily beach change.     

Correlates of burnout among public service lawyers

Several hypotheses suggested by the theoretical literature on burnout were empirically tested in an attempt to identify the organizational conditions associated with employee burnout. Public service lawyers in the U.S. (N= 391) completed a survey designed to assess (a) three components of burnout, namely, emotional exhaustion, depersonalization, and feelings of low personal accomplishment; (b) perceptions of several job conditions predicted to be associated these three components of burnout, including workload, role conflict, social support, decision-making policies, and autonomy; and (c) organizational commitment. Results indicate that emotional exhaustion is most strongly associated with role conflict and quantitative workload. Feelings of personal accomplishment were associated with supervisory social support and job level. Depersonalization was associated with role conflict and decision-making policies. Finally, each burnout component is significantly related to organizational commitment.     

Seasonal variations in activity concentrations of 99Tc and 137Cs in the edible meat fraction of crabs and lobsters from the central Irish Sea

Discharges of most radionuclides into the Irish Sea from the BNFL site at Sellafield have decreased over the past 20 years or so. For a few radionuclides, however, discharges have peaked more recently. Notably, operation of the Enhanced Actinide Removal Plant (EARP) since 1994 has led to an increase in discharges of (99)Tc, as a result of the treatment of previously stored waste, with consequent increases in (99)Tc activity concentrations in a number of marine species, particularly in crustaceans such as lobsters. Previous research has considered the significance of factors such as sex and body weight on radionuclide concentrations. The current project set out to investigate whether seasonal variations in radionuclide concentrations in crabs and lobsters occur, with particular emphasis on the dynamics of (99)Tc and (137)Cs. Organisms were obtained from a site off the Isle of Man, where radionuclide concentrations were measurable but the site was sufficiently distant from Sellafield that the radionuclides were well mixed in the water column and not likely to be influenced by the pulsed nature of discharges of (99)Tc. Crab and lobster samples were collected monthly, between February 2000 and February 2001. Fifteen or 16 individuals (evenly split as male and female) of each species were collected on each occasion. Seawater samples were also collected over the 12-month period. Activity concentrations of (99)Tc in the edible meat fraction (both brown and white meat) ranged from 0.23 to 2.46 Bq kg(-1) (fresh weight (fw)) in crabs and 124 to 216 Bq kg(-1) (fw) in lobsters, with no observed seasonal variations. Activity concentrations of (137)Cs in both crab and lobster were lower, ranging from <0.16 to 0.85 Bq kg(-1) for crab meat (fw) and <0.3 to 3.3 Bq kg(-1) for lobster meat (fw). A statistically significant increase in activity concentrations of (137)Cs in the meat was observed in the summer months for both crab and lobster. The cause has not been investigated but may be related to the laying down of energy reserves during the active feeding period over the summer. At all times, uptake of (99)Tc is higher in the brown meat fraction of both crabs and lobsters, whilst (137)Cs is more uniformly distributed. These results are used to discuss the implications for sampling and monitoring programmes.     

Changes in hydrology and salinity accompanying a century of agricultural conversion in Argentina

Conversions of natural woodlands to agriculture can alter the hydrologic balance, aquifer recharge, and salinity of soils and groundwater in ways that influence productivity and sustainable land use. Using a land-use change chronosequence in semiarid woodlands of Argentina's Espinal province, we examined the distribution of moisture and solutes and estimated recharge rates on adjacent plots of native woodlands and rain-fed agriculture converted 6-90 years previously. Soil coring and geoelectrical profiling confirmed the presence of spatially extensive salt accumulations in dry woodlands and pervasive salt losses in areas converted to agriculture. A 1.1-km-long electrical resistivity transect traversing woodland, 70-year-old agriculture, and woodland, for instance, revealed a low-resistivity (high-salinity) horizon between approximately 3 m and 13 m depth in the woodlands that was virtually absent in the agricultural site because of leaching. Nine-meter-deep soil profiles indicated a 53% increase in soil water storage after 30 or more years of cultivation. Conservative groundwater-recharge estimates based on chloride tracer methods in agricultural plots ranged from approximately 12 to 45 mm/yr, a substantial increase from the <1 mm/yr recharge in dry woodlands. The onset of deep soil moisture drainage and increased recharge led to >95% loss of sulfate and chloride ions from the shallow vadose zone in most agriculture plots. These losses correspond to over 100 Mg of sulfate and chloride salts potentially released to the region's groundwater aquifers through time with each hectare of deforestation, including a capacity to increase groundwater salinity to >4000 mg/L from these ions alone. Similarities between our findings and those of the dryland salinity problems of deforested woodlands in Australia suggest an important warning about the potential ecohydrological risks brought by the current wave of deforestation in the Espinal and other regions of South America and the world.