A CALIBRATION PROCEDURE USING TOPMODEL TO DETERMINE SUITABILITY FOR EVALUATING POTENTIAL CLIMATE CHANGE EFFECTS ON WATER YIELD1

ABSTRACT: An evaluation was conducted on three forested upland watersheds in the northeastern U.S. to test the suitability of TOPMODEL for predicting water yield over a wide range of climatic scenarios. The analysis provides insight of the usefulness of TOPMODEL as a predictive tool for future assessments of potential long-term changes in water yield as a result of changes in global climate. The evaluation was conducted by developing a calibration procedure to simulate a range of climatic extremes using historical temperature, precipitation, and streamfiow records for years having wet, average, and dry precipitation amounts from the Leading Ridge (Pennsylvania), Fernow (West Virginia), and Hubbard Brook (New Hampshire) Experimental Watersheds. This strategy was chosen to determine whether the model could be successfully calibrated over a broad range of soil moisture conditions with the assumption that this would be representative of the sensitivity necessary to predict changes in streamfiow under a variety of climate change scenarios. The model calibration was limited to a daily time step, yet performed reasonably well for each watershed. Model efficiency, a least squares measure of how well a model performs, averaged between 0.64 and 0.78. A simple test of the model whereby daily temperatures were increased by 1.7°C, resulted in annual water yield decreases of 4 to 15 percent on the three watersheds. Although these results makes the assumption that the model components adequately describe the system, this version of TOPMODEL is capable to predict water yield impacts given subtle changes in the temperature regime. This suggests that adequate representations of the effects of climate change on water yield for regional assessment purposes can be expected using the TOPMODEL concept.     

INTEGRATING SOCIAL BENEFIT COST ACCOUNTING INTO WATERSHED RESTORATION AND PROTECTION PROGRAMS1

ABSTRACT: Successful watershed management requires consideration of multiple objectives and the efficient use of scarce public and private resources. One way to address these multi-faceted issues is through Social Benefit-Cost Accounting (SBCA). SBCA is a systematic method of addressing complex social and economic issues relevant to proposed watershed management projects. Benefits of using this technique include: benefits and costs of watershed projects are better understood; politically sensitive issues tend to be put into perspective; and stakeholders' interests are placed on a level playing field. An example from Bogota, Colombia demonstrates how SBCA can be used to value the benefits and costs of a proposed project. By addressing the benefits and costs to all stakeholders, the design of watershed management programs can be improved to achieve goals in a cost-effective manner.     

BSENEFICIAL USE POTENTIAL OF DRY WEATHER FLOW IN THE LAS VEGAS VALLEY,NEVADA1

ABSTRACT: Historically ephemeral washes in the Las Vegas Valley have become perennial streams in the urbanized area, and the primary source of these perennial flows appears to be the overirrigation of ornamental landscaping and turf. Overirrigation produces direct runoff to the washes via the streets and results in high ground water levels in some areas. Elevated ground water levels result in discharge to the washes because of changes in the natural balance of the hydrologic system and construction site and foundation dewatering. In recognition of the resource potential of these flows within the Las Vegas Valley, of the potential for dry weather flows to convey pollutants from the Valley to Lake Mead, and of the need to characterize dry weather flows under the stormwater discharge permit program, the quantity and quality of dry weather flow in Flamingo Wash was investigated during the period September 1990 through May 1993. This paper focuses on the resource potential of the flow (quantity and quality) as it relates to the interception and use of this water within the Valley. Economic and legal issues associated with the interception and use of this resource are not considered here.     

Recovery of Sediment Characteristics in Moraine,Headwater Streams of Northern Minnesota After Forest Harvest1

Merten, Eric C., Nathaniel A. Hemstad, Randall K. Kolka, Raymond M. Newman, Elon S. Verry, and Bruce Vondracek, 2010. Recovery of Sediment Characteristics in Moraine, Headwater Streams of Northern Minnesota After Forest Harvest. Journal of the American Water Resources Association (JAWRA) 46(4): 733-743. DOI: 10.1111/j.1752-1688.2010.00445.x Abstract: We investigated the recovery of sediment characteristics in four moraine, headwater streams in north-central Minnesota after forest harvest. We examined changes in fine sediment levels from 1997 (preharvest) to 2007 (10 years postharvest) at study plots with upland clear felling and riparian thinning, using canopy cover, proportion of unstable banks, surficial fine substrates, residual pool depth, and streambed depth of refusal as response variables. Basin-scale year effects were significant (p < 0.001) for all responses when evaluated by repeated-measures ANOVAs. Throughout the study area, unstable banks increased for several years postharvest, coinciding with an increase in windthrow and fine sediment. Increased unstable banks may have been caused by forest harvest equipment, increased windthrow and exposure of rootwads, or increased discharge and bank scour. Fine sediment in the channels did not recover by summer 2007, even though canopy cover and unstable banks had returned to 1997 levels. After several storm events in fall 2007, 10 years after the initial sediment input, fine sediment was flushed from the channels and returned to 1997 levels. Although our study design did not discern the source of the initial sediment inputs (e.g., forest harvest, road crossings, other natural causes), we have shown that moraine, headwater streams can require an extended period (up to 10 years) and enabling event (e.g., high storm flows) to recover from large inputs of fine sediment.     

Effects of Short- and Long-Term Disturbance Resulting from Military Maneuvers on Vegetation and Soils in a Mixed Prairie Area

Loss of grassland species resulting from activities such as off-road vehicle use increases the need for models that predict effects of anthropogenic disturbance. The relationship of disturbance by military training to plant species richness and composition on two soils (Foard and Lawton) in a mixed prairie area was investigated. Track cover (cover of vehicle disturbance to the soil) and soil organic carbon were selected as measures of short- and long-term disturbance, respectively. Soil and vegetation data, collected in 1-m² quadrats, were analyzed at three spatial scales (60, 10, and 1 m²). Plant species richness peaked at intermediate levels of soil organic carbon at the 10-m² and 1-m² spatial scales on both the Lawton and Foard soils, and at intermediate levels of track cover at all three spatial scales on the Foard soil. Species composition differed across the disturbance gradient on the Foard soil but not on the Lawton soil. Disturbance increased total plant species richness on the Foard soil. The authors conclude that disturbance up to intermediate levels can be used to maintain biodiversity by enriching the plant species pool.     

Neurophysiological Effects Induced in the Nervous Tissue by Low-Frequency, Pulsed Magnetic Fields

Summary The influence of pulsed magnetic fields (PMF) on the properties of nervous tissue was investigated. Hippocampal slices or synaptosomes obtained from hippocampal tissue were used as model systems. The amplitude of potentials recorded in vitro from one of the hippocampal pathways (Schaffer collaterals that use glutamate as a neurotransmitter) was employed as a measure of the influence of magnetic fields on synaptic efficiency. The synaptic glutamate turnover and radioactive calcium accumulation were used as markers of the PMF influence on biochemistry of synaptic mechanisms. The exposure of hippocampal slices for 30 min to PMF amplified evoked potentials. While the frequency of 0.16 Hz exerted the strongest effect, lower (0.01, 0.07, 0.03 Hz) and higher (0.5 Hz) frequencies were much less effective. The enhancement of the neuronal excitability was correlated with significant increase in the neuronal spontaneous activity mediated by electrical synapses. The PMF-induced changes in the excitability of the tissue were accompanied by an increase in the synaptic turnover of glutamate. The release of radioactive D-Aspartate (a glutamate analog used as a marker for glutamate turnover) from the slices, and its uptake by synaptosomes were enhanced, and reduced respectively, following the stimulation with pulsed magnetic fields. The frequency which was the most efficient in amplification of evoked potentials (0.16 Hz) was also the most effective in the modulation of the release and uptake processes. The PMF-induced changes in neurotransmitter turnover coincided with an increase in ⁴⁵Ca²⁺ accumulation observed in hippocampal slices exposed to PMF.     

Techniques for accuracy assessment of tree locations extracted from remotely sensed imagery

Remotely sensed imagery is becoming a common source of environmental data. Consequently, there is an increasing need for tools to assess the accuracy and information content of such data. Particularly when the spatial resolution of imagery is fine, the accuracy of image processing is determined by comparisons with field data. However, the nature of error is more difficult to assess. In this paper we describe a set of tools intended for such an assessment when tree objects are extracted and field data are available for comparison. These techniques are demonstrated on individual tree locations extracted from an IKONOS image via local maximum filtering. The locations of the extracted trees are compared with field data to determine the number of found and missed trees. Aspatial and spatial (Voronoi) analysis methods are used to examine the nature of errors by searching for trends in characteristics of found and missed trees. As well, analysis is conducted to assess the information content of found trees.     

In situ measurements of nitrate leaching implicate poor nitrogen and irrigation management on sandy soils

Minimizing the risk of nitrate contamination along the waterways of the U.S. Great Plains is essential to continued irrigated corn production and quality water supplies. The objectives of this study were to quantify nitrate (NO(3)) leaching for irrigated sandy soils (Pratt loamy fine sand [sandy, mixed, mesic Lamellic Haplustalfs]) and to evaluate the effects of N fertilizer and irrigation management strategies on NO(3) leaching in irrigated corn. Two irrigation schedules (1.0x and 1.25x optimum) were combined with six N fertilizer treatments broadcast as NH(4)NO(3) (kg N ha(-1)): 300 and 250 applied pre-plant; 250 applied pre-plant and sidedress; 185 applied pre-plant and sidedress; 125 applied pre-plant and sidedress; and 0. Porous-cup tensiometers and solution samplers were installed in each of the four highest N treatments. Soil solution samples were collected during the 2001 and 2002 growing seasons. Maximum corn grain yield was achieved with 125 or 185 kg N ha(-1), regardless of the irrigation schedule (IS). The 1.25x IS exacerbated the amount of NO(3) leached below the 152-cm depth in the preplant N treatments, with a mean of 146 kg N ha(-1) for the 250 and 300 kg N preplant applications compared with 12 kg N ha(-1) for the same N treatments and 1.0x IS. With 185 kg N ha(-1), the 1.25x IS treatment resulted in 74 kg N ha(-1) leached compared with 10 kg N ha(-1) for the 1.0x IS. Appropriate irrigation scheduling and N fertilizer rates are essential to improving N management practices on these sandy soils.     

Quantifying the impact of regular cutting on vegetative buffer efficacy for nitrogen-15 sequestration

This study used the stable 15N isotope to quantitatively examine the effects of cutting on vegetative buffer uptake of NO3(-)-N based on the theory that regular cutting would increase N demand and sequestration by encouraging new plant growth. During the summer of 2002, 10 buffer plots were established within a flood-irrigated pasture. In 2003, 15N-labeled KNO3 was applied to the pasture area at a rate of 5 kg N ha(-1) and 99.7 atom % 15N. One-half of the buffer plots were trimmed monthly. In the buffers, the cutting effect was not significant in the first few weeks following 15N application, with both the cut and uncut buffers sequestering 15N. Over the irrigation season, however, cut buffers sequestered 2.3 times the 15N of uncut buffers, corresponding to an increase in aboveground biomass following cutting. Cutting and removing vegetation allowed the standing biomass to take advantage of soil 15N as it was released by microbial mineralization. In contrast, the uncut buffers showed very little change in 15N sequestration or biomass, suggesting senescence and a corresponding decrease in N demand. Overall, cutting significantly improved 15N attenuation from both surface and subsurface water. However, the effect was temporally related, and only became significant 21 to 42 d after 15N application. The dominant influence on runoff water quality from irrigated pasture remains irrigation rate, as reducing the rate by 75% relative to the typical rate resulted in a 50% decrease in total runoff losses and a sevenfold decrease in 15N concentration.     

Runoff phosphorus losses from surface-applied biosolids

Runoff losses of dissolved and particulate phosphorus (P) may occur when rainfall interacts with manures and biosolids spread on the soil surface. This study compared P levels in runoff losses from soils amended with several P sources, including 10 different biosolids and dairy manure (untreated and treated with Fe or Al salts). Simulated rainfall (71 mm h(-1)) was applied until 30 min of runoff was collected from soil boxes (100 x 20 x 5 cm) to which the P sources were surfaced applied. Materials were applied to achieve a common plant available nitrogen (PAN) rate of 134 kg PAN ha(-1), resulting in total P loading rates from 122 (dairy manure) to 555 (Syracuse N-Viro biosolids) kg P ha(-1). Two biosolids produced via biological phosphorus removal (BPR) wastewater treatment resulted in the highest total dissolved phosphorus (13-21.5 mg TDP L(-1)) and total phosphorus (18-27.5 mg TP L(-1)) concentrations in runoff, followed by untreated dairy manure that had statistically (p = 0.05) higher TDP (8.5 mg L(-1)) and TP (10.9 mg L(-1)) than seven of the eight other biosolids. The TDP and TP in runoff from six biosolids did not differ significantly from unamended control (0.03 mg TDP L(-1); 0.95 mg TP L(-1)). Highest runoff TDP was associated with P sources low in Al and Fe. Amending dairy manure with Al and Fe salts at 1:1 metal-to-P molar ratio reduced runoff TP to control levels. Runoff TDP and TP were not positively correlated to TP application rate unless modified by a weighting factor reflecting the relative solubility of the P source. This suggests site assessment indices should account for the differential solubility of the applied P source to accurately predict the risk of P loss from the wide variety of biosolids materials routinely land applied.