Do natural resources and economic components exhibit differential quantile environmental effects?

In view of the resource curse assumption, the environmental aspects of resource utilization are arguably posing more dangers to human existence. In the Middle East and North Africa (MENA) region, the region that holds more than 60% and 50% of the world's oil and gas reserves respectively, the need to examine the contribution of natural resources to environmental quality among other factors cannot be overemphasized. By leveraging on the novelty of observing the differential impact of natural resources and other economic components such as income and primary energy utilizations across the quantiles of carbon emission, this study implements the quantile regression approach alongside other relevant techniques to analyze data between 1990 and 2018 for selected countries in the MENA region including Saudi Arabia, Iran, Kuwait, Qatar, Algeria, Morocco, Oman, Egypt, and the United Arab Emirates (UAE). The result posits that natural resource utilization generally hampers the environment across the quantiles. However, this negative effect decreases until the 50th quantile before starting to rise again toward the upper quantiles. Additionally, primary energy utilization and globalization respectively worsen and improve environmental quantile, especially toward the upper quantiles while income affirms the inverted U-shaped hypothesis across the entire quantiles. Moreover, there is a statistically significant one-way directional causality from natural resources, economic expansion, primary energy use, and globalization to carbon emission levels. Hence, the study offers environmentally friendly resource utilization policies to the MENA economies and other resource-rich states by extension.     

The Influence of the Pacific Decadal Oscillation on Annual Floods in the Rivers of Western Canada

We analyzed annual peak flow series from 127 naturally flowing or naturalized streamflow gauges across western Canada to examine the impact of the Pacific Decadal Oscillation (PDO) on annual flood risk, which has been previously unexamined in detail. Using Spearman's rank correlation ρ and permutation tests on quantile‐quantile plots, we show that higher magnitude floods are more likely during the negative phase of the PDO than during the positive phase (shown at 38% of the stations by Spearman's rank correlations and at 51% of the stations according to the permutation tests). Flood frequency analysis (FFA) stratified according to PDO phase suggests that higher magnitude floods may also occur more frequently during the negative PDO phase than during the positive phase. Our results hold throughout much of this region, with the upper Fraser River Basin, the Columbia River Basin, and the North Saskatchewan River Basin particularly subject to this effect. Our results add to other researchers' work questioning the wholesale validity of the key assumption in FFA that the annual peak flow series at a site is independently and identically distributed. Hence, knowledge of large‐scale climate state should be considered prior to the design and construction of infrastructure.     

FLOOD FREQUENCY ANALYSIS FOR EVALUATING WATERSHED CONDITIONS WITh RAINFALL-RUNOFF MODELS1

ABSTRACT: Many rainfall-runoff modeling studies compare flood quantiles for different land-use and/or flood mitigation scenarios. However, when flood quantiles are estimated using conventional statistical methods, comparisons may be misleading because the estimates often misrepresent the quantile relationship between scenarios. An alternate statistical procedure is proposed, in which rainfall-runoff modeling is used to evaluate an approximate relationship between flood quantiles for different scenarios. Monte Carlo experiments show that the proposed method produces flood quantile estimates that better reflect the differences between scenarios. The ratio between quantiles for different scenarios is more accurate, so comparisons of the scenarios using flood quantiles are more reliable.     

SPATIAL COMPARABILITY OF THE PALMER DROUGHT SEVERITY INDEX1

ABSTRACT: The Palmer Drought Severity Index, which is intended to be of reasonable comparable local significance both in space and time, has been extensively used as a measure of drought for both agricultural and water resource management. This study examines the spatial comparability of Palmer's (1965) definition of severe and extreme drought. Index values have been computed for 1035 sites with at least 60 years of record that are scattered across the contiguous United States, and quantile values corresponding to a specified index value were calculated for given months and then mapped. The analyses show that severe or extreme droughts, as defined by Palmer (1965), are not spatially comparable in terms of identifying rare events. The wide variation across the country in the frequency of occurrence of Palmer's (1965) extreme droughts reflects the differences in the variability of precipitation, as well as the average amount of precipitation. It is recommended first, that a drought index be developed which considers both variability and averages; and second, that water resource managers and planners define a drought in terms of an index value that corresponds to the expected quantile (return period) of the event.     

A COMPARISON OF HAND- AND SPLINE-DRAWN PRECIPITATION MAPS FOR MOUNTAINOUS MONTANA1

ABSTRACT: Average annual precipitation for the period 1961–1990 was estimated for a mountainous region in Montana with a Laplacian thin-plate spline (ANUSPLIN) and compared to a hand-drawn map. Input data included latitude, longitude, and elevation from a three-arc-second U.S. Geological Survey Digital Elevation Model of the Bozeman and Billings 1 × 2 topographic quadrangles and precipitation data at 96 stations. The two maps are similar in appearance. Digital comparison of the two maps with ARC/INFO's Grid tools shows that mean annual precipitation for the hand-contoured map is 22.9 inches and for the ANUSPLIN map is 23.7 inches. Of the 5,760,000 cells, 53 percent showed no difference between ANUSPLIN and hand-drawn maps; 19 percent showed a two-inch difference, and 28 percent showed more than 2 inches difference. Input data and model output at the same location are not different (standard deviation 1.77, p-value 0.76). Hand-drawn maps show two inches more precipitation during the 1961–90 period than during the 1941–1970 period. Similarly, measured data at 73 sites for the period 1961–1990 are on average 2.4 inches higher than the same stations during the 1941–1970 period. The difference is significant (p-value > 0.0001).     

THE ATMOSPHERIC WATER BALANCE AND THE HYDROLOGY OF LARGE RIVER BASINS1

The concept of using the atmospheric water balance technique in the study of the hydrology of large (greater than 10⁵km²) river basins is described. The atmospheric water balance technique consists of determining the spacial and time distributions and fluxes of water vapor through the atmospheric volume overlying the basin. The quantity precipitation minus evaporation at the earth's surface is determined as a residual of the computation. A review of the results of various experiments employing this technique is provided. The incorporation of the technique in a study of the hydrology of a large river basin is demonstrated by showing the results of a study of the hydrometeorology of the Upper Colorado River Basin. The example covers the study of eleven winter seasons, November through April, 1957–1968. The seasonal accumulation of water over the basin as determined by the atmospheric water balance is highly correlated with annual runoff. Correlation coefficient r = .8. The daily evaporation rate during dry days varies by a factor of two over the winter season, and is shown to be related to the incoming solar radiation intensity.     

QUALITY OF 1995 SPRING TOTAL DISSOLVED GAS DATA: COLUMBIA AND SNAKE RWERS1

ABSTRACT: The quality of the U.S. Army Corps of Engineers' (Corps) total dissolved gas (TDG) data base for the 1995 spring spill season was reviewed to determine the value of this information in real-time management decisions regarding river operations. We concluded that problems in transmitting, archiving, correcting and interpreting the records constitute significant sources of data anomalies that affect the accuracy and reliability of information necessary to manage spill and TDG in the Columbia and Snake rivers. The data base that was reviewed covers 25 selected Columbia and Snake river stations, and includes real-time TDG data needed to regulate spill operations to maintain gas levels within state water quality standards and to monitor effects on fish and aquatic life during the salmon migration season. A wide range of anomalies (daily averages missing or in error or based on incomplete records) was detected in more than one-third (37 percent) of the Corps' gas data base. Extreme anomalies (daily averages including errors and discontinuities for more than eight hours in a day) were found in 16 percent of the data base. The Fish Passage Center, also reviewed the Corps' data and reported an overall 33 percent incidence of anomalous days. Despite arriving at similar findings about the Corps' data base, we detected a 28 percent discrepancy in the type of data anomalies between our analyses. Real. time improvements in the quality of the dissolved gas data base are necessary to provide managers with a reliable product from this monitoring effort.     

Soil nitrate nitrogen dynamics after biosolids application in a tobosagrass desert grassland

Dormant-season application of biosolids increases desert grass production more than growing season application in the first growing season after application. Differential patterns of NO3-N (plant available N) release following seasonal biosolids application may explain this response. Experiments were conducted to determine soil nitrate nitrogen dynamics following application of biosolids during two seasons in a tobosagrass [Hilaria mutica (Buckl.) Benth.] Chihuahuan Desert grassland. Biosolids were applied either in the dormant (early April) or growing (early July) season at 0, 18, or 34 dry Mg ha(-1). A polyester-nylon mulch was also applied to serve as a control that approximated the same physical effects on the soil surface as the biosolids but without any chemical effects. Supplemental irrigation was applied to half of the plots. Soil NO3-N was measured at two depths (0-5 and 5-15 cm) underneath biosolids (or mulch) and in interspace positions relative to surface location of biosolids (or mulch). Dormant-season biosolids application significantly increased soil NO3-N during the first growing season, and also increased soil NO3-N throughout the first growing season compared to growing-season biosolids application in a year of higher-than-average spring precipitation. In a year of lower-than-average spring precipitation, season of application did not affect soil NO3-N. Soil NO3-N was higher at both biosolids rates for both seasons of application than in the control treatment. Biosolids increased soil NO3-N compared to the inert mulch. Irrigation did not significantly affect soil NO3-N. Soil NO3-N was not significantly different underneath biosolids and in interspace positions. Surface soil NO3-N was higher during the first year of biosolids application, and subsurface soil NO3-N increased during the second year. Results showed that biosolids rate and season of application affected soil NO3-N measured during the growing season. Under dry spring-normal summer precipitation conditions, season of application did not affect soil NO3-N; in contrast, dormant season application increased soil NO3-N more than growing season application under wet spring-dry summer conditions.     

近50年新疆沙尘暴频率时空变化趋势分析

采用新疆54个气象站近50年的气象资料,分析新疆沙尘暴时空分布特征、年际和年内演变趋势及年际演变的影响因素。结果显示：新疆沙尘暴近50年以来空间分布特征是南疆多于北疆,沙尘暴主要出现在3～10月,其中4～7月为高发时段。年际演变趋势20世纪80年代以来较60、70年代都有所减少;80年代以后沙尘暴发生日数减少。     

PATTERNS OF SUSPENDED SEDIMENT TRANSPORT IN A COASTAL ALASKA STREAM1

Suspended sediment data from a 154 ha watershed on northeast Chichagof Island, Alaska, were collected over three fall storm seasons from 1980 to 1982. Sediment rating curves for nine pooled storms explained less than 34 percent of the variation in total suspended solids (TSS). Significantly higher concentrations of suspended sediment occurred during the rising limb of storm hydrographs than for similar flows on the falling limb, accounting for hysteresis loops in TSS versus streamflow plots for individual storms. These hysteresis loops were wider during early season storms, indicating that easily transportable fine sediment may have been flushed from the upper portion of channel banks and from behind large organic debris during early season peak flows. Regression relationships (TSS versus Q) developed for the highest stormflows (> 1 m³/s) had steeper slopes than the lower stormflows (< 1 m³/s). Turbidity correlated well (r=0.94) with TSS for all storm-flow data combined. Organic matter constituted an average of 35 percent (by weight) of TSS for all water quality samples.     

Precipitation Amount and Intensity Trends Across Southwest Saudi Arabia

This study examines precipitation accumulation and intensity trends across a region in southwest Saudi Arabia characterized by distinct seasonal weather patterns and mountainous terrain. The region is an example of an arid/semiarid area faced with maintaining sustainable water resources with a growing population. Annual and seasonal trends in precipitation amount were examined from 29 rain gages divided among four geographically unique regions from 1945/1946 to 2009. Two of the regions displayed significantly declining annual trends over the time series using a Mann‐Kendall test modified for autocorrelation (α < 0.05). Seasonal analysis revealed insignificant declining trends in at least two of the regions during each season. The largest and most consistent declining trends occurred during wintertime where all regions experienced negative trends. Several intensity metrics were examined in the study area from four additional stations containing daily data from 1985 to 2011. Intensity metrics included total precipitation, wet day count, simple intensity index, maximum daily annual rainfall, and upper/lower precipitation distribution changes. In general, no coherent trends were found among the daily stations suggesting precipitation is intensifying across the study area. The work represents the first of its size in the study area, and one of few in the region due to the lack of available long‐term data needed to properly examine precipitation changes.     

TEMPORAL AND SPATIAL CHARACTERIZATION OF RAINFALL OVER CENTRAL AND SOUTH FLORIDA1

requency evaluation and spatial characterization of rainfall in Central and South Florida are presented. Point frequency analysis performed at all available sites has shown that the 2‐parameter Gamma probability density function is the best model for monthly rainfall frequency over Central and South Florida. The model's parameters estimated at 145 stations were used to provide monthly rainfall estimates for 10‐ and 100‐year dry and wet return periods. Experimental and theoretical variograms computed for these estimates, as well as the Kriging estimation variance maps, show that the existing rain gage network is less capable of resolving monthly rainfall variation in the wet season than the dry season. May is the dry‐to‐wet transition month, while October is the wet‐to‐dry transition month with average rainfall of 4.5 inches. Monthly average rainfall is above 7 inches during the wet season and below 3 inches during the dry season. Two‐thirds of the annual rainfall is accumulated in the wet season. Annual average rainfall is maximum (above 60 inches) in many areas along the east coast, and is minimum (below 45 inches) in many areas over Lake Okee‐chobee and Central Florida. Rainfall maps show a changing pattern between the wet and the dry seasons. Frontal rainfall occurs in the dry season, while convective rainfall, tropical depression, and hurricanes occur in the wet season. Average rainfall is higher along the east coast area in the dry season and it is higher along the west coast area in the wet season.     

A PROPOSED MODIFICATION TO REGULATION OF LAKE OKEECHOBEE1

ABSTRACT: The current Lake Okeechobee regulation schedule is two feet higher than previous schedules that were in operation during the early 1970's. Its implementation was in response to prolonged periods of drought that occurred during the 1960's and early 1970's and the large increases in consumptive uses that were projected, and are presently occurring in south Florida. The additional storage provided by the schedule undoubtedly helped prevent more severe water shortages during the record setting 1980–1982 drought. However, two environmental concerns associated with the present schedule surfaced in recent years with the return to more normal rainfall conditions. First, the present schedule allows frequent high water conditions to exist in the lake that appear to be stressful to the unique littoral zone habitat of the lake. Second, the allowable buildup of storage prior to the dry season, combined with the large required decrease in storage prior to the hurricane (wet) season, contribute to the need for large regulation releases to tidewater. These large discharges have undesirable impacts on ecosystems of the downstream estuaries. This paper presents an alternative schedule that better meets the needs of the estuarine habitats without negatively impacting the other objectives of managing the lake.     

The Water‐Year Water Balance of the Colorado River Basin

Model‐estimated monthly water balance components (i.e., potential evapotranspiration, actual evapotranspiration, and runoff (R)) for 146 United States (U.S.) Geological Survey 8‐digit hydrologic units located in the Colorado River Basin (CRB) are used to examine the temporal and spatial variability of the CRB water balance for water years 1901 through 2014 (a water year is the period from October 1 of one year through September 30 of the following year). Results indicate that the CRB can be divided into six subregions with similar temporal variability in monthly R. The water balance analyses indicated that approximately 75% of total water‐year R is generated by just one CRB subregion and that most of the R in the basin is derived from surplus (S) water generated during the months of October through April. Furthermore, the analyses show that temporal variability in S is largely controlled by the occurrence of negative atmospheric pressure anomalies over the northwestern conterminous U.S. (CONUS) and positive atmospheric pressure anomalies over the southeastern CONUS. This combination of atmospheric pressure anomalies results in an anomalous flow of moist air from the North Pacific Ocean into the CRB, particularly the Upper CRB. Additionally, the occurrence of extreme dry and wet periods in the CRB appears to be related to variability of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation.     

A SURVEY OF THE U.S. NATIONAL PRECIPITATION NETWORK1

ABSTRACT: Numbers and record lengths of precipitation stations were surveyed in the conterminous United States using climatological data published in 1975 by the National Weather Service (NWS). The total numbers of nonrecording (8247) and recording (3036) gages were about the same as in the 1940s and less than in the late 1950s; about 70 percent of the nonrecording gages have record lengths of 25 years or more. State network densities were increased exponentially with population density and long term precipitation average. Except for a few states, precipitation stations maintained by the NWS are adequate in numbers to ensure a 95 percent statistical probability that state sample means will estimate true means within ± 5 percent.     

Responses of Soil CO<Subscript>2</Subscript> Efflux to Precipitation Pulses in Two Subtropical Forests in Southern China

This study was designed to examine the responses of soil CO₂ efflux to precipitation pulses of varying intensities using precipitation simulations in two subtropical forests [i.e., mixed and broadleaf forests (MF and BF)] in southern China. The artificial precipitation event was achieved by spraying a known amount of water evenly in a plot (50 × 50 cm²) over a 30 min period, with intensities ranging from 10, 20, 50 and 100 mm within the 30 min. The various intensities were simulated in both dry season (in December 2007) and wet (in May 2008) season. We characterized the dynamic patterns of soil CO₂ efflux rate and environmental factors over the 5 h experimental period. Results showed that both soil moisture and soil CO₂ efflux rate increased to peak values for most of the simulated precipitation treatments, and gradually returned to the pre-irrigation levels after irrigation in two forests. The maximum peak of soil CO₂ efflux rate occurred at the 10 mm precipitation event in the dry season in BF and was about 3.5 times that of the pre-irrigation value. The change in cumulative soil CO₂ efflux following precipitation pulses ranged from −0.68 to 1.72 g CO₂ m⁻² over 5 h compared to the pre-irrigation levels and was generally larger in the dry season than in the wet season. The positive responses of soil CO₂ efflux to precipitation pulses declined with the increases in precipitation intensity, and surprisingly turned to negative when precipitation intensity reached 50 and 100 mm in the wet season. These findings indicated that soil CO₂ efflux could be changed via pulse-like fluxes in subtropical forests in southern China as fewer but extreme precipitation events occur in the future.     

EVALUATION OF NEXRAD STAGE III PRECIPITATION DATA OVER A SEMIARID REGION1

This study examines NEXRAD Stage III product (hourly, cell size 4 km by 4 km) for its ability in estimating precipitation in central New Mexico, a semiarid area. A comparison between Stage III and a network of gauge precipitation estimates during 1995 to 2001 indicates that Stage III (1) overestimates the hourly conditional mean (CM) precipitation by 33 percent in the monsoon season and 55 percent in the nonmonsoon season; (2) overestimates the hourly CM precipitation for concurrent radar‐gauge pairs (nonzero value) by 13 percent in the monsoon season and 6 percent in the nonmonsoon season; (3) overestimates the seasonal precipitation accumulation by 11 to 88 percent in monsoon season and underestimates by 18 to 89 percent in the nonmonsoon season; and (4) either overestimates annual precipitation accumulation up to 28.2 percent or underestimates it up to 11.9 percent. A truncation of 57 to 72 percent of the total rainfall hours is observed in the Stage III data in the nonmonsoon season, which may be the main cause for both the underestimation of the radar rainfall accumulation and the lower conditional probability of radar rainfall detection in the nonmonsoon season. The study results indicate that the truncation caused loss of small rainfall amounts (events) is not effectively corrected by the real‐time rain gauge calibration that can adjust the rainfall rates but cannot recover the truncated small rainfall events. However, the truncation error in the monsoon season may be suppressed due to the larger rainfall rate and/or combined effect of overestimates by bright band and hail contaminations, virga, advection, etc. In general, improvement in NEXRAD performance since the monsoon season in 1998 is observed, which is consistent with the systematic improvement in the NEXRAD network.     

Evidence for Changing Flood Risk in New England Since the Late 20th Century1

Abstract: Long‐term flow records for watersheds with minimal human influence have shown trends in recent decades toward increasing streamflow at regional and national scales, especially for low flow quantiles like the annual minimum and annual median flows. Trends for high flow quantiles are less clear, despite recent research showing increased precipitation in the conterminous United States over the last century that has been brought about primarily by an increased frequency and intensity of events in the upper 10th percentile of the daily precipitation distribution – particularly in the Northeast. This study investigates trends in 28 long‐term annual flood series for New England watersheds with dominantly natural streamflow. The flood series are an average of 75 years in length and are continuous through 2006. Twenty‐five series show upward trends via the nonparametric Mann‐Kendall test, 40% (10) of which are statistically significant (p < 0.1). Moreover, an average standardized departures series for 23 of the study gages indicates that increasing flood magnitudes in New England occurred as a step change around 1970. The timing of this is broadly synchronous with a phase change in the low frequency variability of the North Atlantic Oscillation, a prominent upper atmospheric circulation pattern that is known to effect climate variability along the United States east coast. Identifiable hydroclimatic shifts should be considered when the affected flow records are used for flood frequency analyses. Special treatment of the flood series can improve the analyses and provide better estimates of flood magnitudes and frequencies under the prevailing hydroclimatic condition.     

Impacts of Climate Change on Extreme Precipitation Events Over Flamingo Tropicana Watershed1

Abstract: Climate change, particularly the projected changes to precipitation patterns, is likely to affect runoff both regionally and temporally. Extreme rainfall events are expected to become more intense in the future in arid urban areas and this will likely lead to higher streamflow. Through hydrological modeling, this article simulates an urban basin response to the most intense storm under anthropogenic climate change conditions. This study performs an event‐based simulation for shorter duration storms in the Flamingo Tropicana (FT) watershed in Las Vegas, Nevada. An extreme storm, defined as a 100‐year return period storm, is selected from historical records and perturbed to future climatic conditions with respect to multimodel multiscenario (A1B, A2, B1) bias corrected and spatially disaggregated data from the World Climate Research Programme's (WCRP's) database. The cumulative annual precipitation for each 30‐year period shows a continuous decrease from 2011 to 2099; however, the summer convective storms, which are considered as extreme storms for the study area, are expected to be more intense in future. Extreme storm events show larger changes in streamflow under different climate scenarios and time periods. The simulated peak streamflow and total runoff volume shows an increase from 40% to more than 150% (during 2041‐2099) for different climate scenarios. This type of analysis can help evaluate the vulnerability of existing flood control system and flood control policies.