Saturation Deficit Research Articles

Simulating Soil-Water Movement through Loess-Veneered Landscapes Using Nonconsilient Saturated Hydraulic Conductivity Measurements

Soil Survey Geographic Database (SSURGO) data are available for the entire United States, so are incorporated in many regional and national models of hydrology and environmental management. However, SSURGO does not provide an understanding of spatial variability and only includes saturat- ed hydraulic conductivity (K sat ) values estimated from particle size analysis (PSA). This study showed model sensitivity to the substitution of SSURGO data with locally described soil properties or alternate methods of measur- ing K sat . Incorporation of these different soil data sets significantly changed the results of hydrologic modeling as a consequence of the amount of space available to store soil water and how this soil water is moved downslope. Locally described soil profiles indicated a difference in K sat when measured in the field vs. being estimated from PSA. This, in turn, caused a differ - ence in which soil layers were incorporated in the hydrologic simulations using TOPMODEL, ultimately affecting how soil water storage was simu- lated. Simulations of free-flowing soil water, the amount of water traveling through pores too large to retain water against gravity, were compared with field observations of water in wells at five slope positions along a cat- ena. Comparison of the simulated data with the observed data showed that the ability to model the range of conditions observed in the field varied as a function of three soil data sets (SSURGO and local field descriptions using PSA-derived K sat or field-measured K sat ) and that comparison of absolute values of soil water storage are not valid if different characterizations of soil properties are used. Abbreviations: AET, actual evapotranspiration; CCHP, compact constant-head permeameter; DEM, digital elevation model; FC, field capacity; PSA, particle size analysis; PSAf, particle size analysis derived from field data; SD, saturation deficit; SSURGO, Soil Survey Geographic Database; TWI, topographic wetness index.

Solar dryer efficiency considering the total drying potential. Application of this potential as a resource indicator in north-western Argentina

Indicators of drying potential for a region based on a model of free water evaporation in a solar dryer are presented. In these indicators, the total solar radiation and the saturation deficit of ambient air are considered as driving forces for solar drying process. The indicators were used to define the solar dryer performance considering the drying potential of the site. The performance definition was applied to a forced solar dryer placed in the town of San Carlos, (Salta, north-western Argentina) and was loaded with 30kg of trays filled with water. The results were compared with other performance definitions. A standard dryer of 0.1kgs−1 airflow was defined to estimate the potential indicators for 18 locations of the north-western Argentina using daily historical data. A mapping of dryer potential was obtained for the entire region through interpolating of results, showing similarity in relation to the distribution of phytogeographic areas. September was the month with the highest potential for solar drying on account of the end of the dried season and the influence of the local warm wind. The indicators also were obtained for San Carlos using recently measured data. Deviations from these potentials with respect to those obtained from the historical database were analyzed and similar results were obtained. The usefulness of these indicators was showed as a tool to be considered when variables other than solar radiation – such as temperature and relative humidity – are taken as energy sources.

Influence of selected meteorological variables on the questing activity of Ixodes ricinus ticks in Lower Silesia, SW Poland.

The relationship between climate data and tick questing activity is crucial for estimation of the spatial and temporal distribution of the risk of ticks and tick-borne diseases. This study establishes correlations between selected meteorological variables provided by the Weather Research and Forecasting model (WRF) and the questing activity of Ixodes ricinus nymphs and adults on a regional scale across Lower Silesia, Poland. Application of Generalized Linear Mixed Models (GLMM), built separately for adults and nymphs, showed that solar radiation, air temperature, and saturation deficit appeared to be the meteorological variables of prime importance, whereas the wind speed was less important. However, the effect of meteorological parameters was different for adults and nymphs. The adults are also more influenced by forest cover and the percentage of forest type if compared to nymphs. The WRF model providing meteorological variables separately for each location and day of tick sampling can be useful in studies of questing activity of ticks on a regional scale.

Impact of upstream flow conditions on the initiation of moist convection over the island of Corsica

The influence of upstream flow on the initiation of moist convection over Corsica is investigated using semi-idealized simulations. The simulations, performed with the Consortium for Small-scale Modeling (COSMO) model, are initialized with one vertical profile at all grid points and under constant boundary conditions. The upstream wind velocity and wind direction, as well as the saturation deficit and stability, are systematically varied to estimate the impact of the individual factors on the initiation and strength of moist convection. Also, the influence of radiation is evaluated. It is found that deep convection can only develop with high solar radiation. With lower radiation, thermal wind systems are weak, and only shallow convection is triggered. Results show that with strong solar radiation, a strong upstream wind velocity is less efficient in triggering deep convection than a weaker one. This is due to the dynamic effects on the flow field. A low upstream wind velocity enables thermal wind systems to become dominant and the preconvective conditions for deep convection are more favorable. This leads to more events with deep convection and precipitation. The wind direction can be the determining factor for the initiation of deep convection and also controls the location of precipitation. A change of just 15° can decide on whether deep convection occurs or not. With a high upstream wind velocity, the location is always on the lee side of the island. With a lower upstream wind velocity, two hot spots for convection initiation, one in the northern central part and one in the western part of the island, are identified. It is further found that the impact of saturation deficit is higher than the impact of stability. With increased instability, the atmospheric conditions are more favorable for the development of convection, but the high saturation deficit in the middle troposphere prevents the formation of deep convection. Through reduction of the saturation deficit, multiple convective cells can develop in the more humid atmosphere. Additionally, the integrated water vapor is larger, which means that more precipitable water is available allowing larger amounts of precipitation.

Estimating the organic carbon stabilisation capacity and saturation deficit of soils: a New Zealand case study

The capacity of a soil to sequester organic carbon can, in theory, be estimated as the difference between the existing soil organic C (SOC) concentration and the SOC saturation value. The C saturation concept assumes that each soil has a maximum SOC storage capacity, which is primarily determined by the characteristics of the fine mineral fraction (i.e. 0. The median saturation deficit for both Allophanic and non-Allophanic soils was 12 mg C g−1 at 0–15 cm depth and 15 mg C g−1 at 15–30 cm depths. Improving predictions of the saturation deficit of soils may be important to developing and deploying effective SOC sequestration strategies.

Does consideration of water routing affect simulated water and carbon dynamics in terrestrial ecosystems?

Abstract. The cycling of carbon (C) in terrestrial ecosystems is closely coupled with the cycling of water. An important mechanism connecting ecological and hydrological processes in terrestrial ecosystems is lateral flow of water along landscapes. Few studies, however, have examined explicitly how consideration of water routing affects simulated water and C dynamics in terrestrial ecosystems. The objective of this study is to explore how consideration of water routing in a process-based hydro-ecological model affects simulated water and C dynamics. To achieve that end, we rasterized the regional hydro-ecological simulation system (RHESSys) and employed the rasterized RHESSys (R-RHESSys) in a forested watershed. We performed and compared two contrasting simulations, one with and another without water routing. We found that R-RHESSys was able to correctly simulate major hydrological and ecological variables regardless of whether water routing was considered. When water routing was considered, however, soil water table depth and saturation deficit were simulated to be greater and spatially more heterogeneous. As a result, water (evaporation, transpiration, and evapotranspiration) and C (forest productivity, soil autotrophic and heterotrophic respiration) fluxes also were simulated to be spatially more heterogeneous compared to the simulation without water routing. When averaged for the entire watershed, the three simulated water fluxes were greater while C fluxes were smaller under simulation considering water routing compared to that ignoring water routing. In addition, the effects of consideration of water routing on simulated C and water dynamics were more apparent in dry conditions. Overall, the study demonstrated that consideration of water routing enabled R-RHESSys to better capture our preconception of the spatial patterns of water table depth and saturation deficit across the watershed. Because soil moisture is fundamental to the exchange of water and C fluxes among soil, vegetation and the atmosphere, ecosystem and C cycle models therefore need to explicitly represent water routing in order to accurately quantify the magnitude and patterns of water and C fluxes in terrestrial ecosystems.

Changing precipitation regimes and the water and carbon economies of trees

Climate change is predicted to affect the water balance of several ecosystems mostly through changes in the energy budget and hydrological input (rainfall frequency, intensity, and timing). Changes in rainfall patterns and cloudiness directly affect incoming radiation, atmospheric water vapor saturation deficit and soil water availability, the main variables controlling the rates of water uptake and transport along the soil–plant–atmosphere continuum (SPAC). Developing a predictive framework about vegetation responses to a changing climate is challenging because it involves complex non-linear interactions between these environmental variables and species-specific responses. By examining the hydraulic traits of functional groups within plant communities we can better predict the impacts of changes in rainfall regimes within functional groups and therefore, generate more realistic predictions of ecosystem carbon and water balance changes due to local and regional changes in precipitation regimes. In this review, we discuss several aspects of plant hydraulic functioning and then explore how predicted changes in precipitation regimes may affect tree water and carbon balance. We examine the impacts of changes in rainfall patterns on the SPAC and also explore the multiple ways that plants can absorb and transport water. Finally, we explore the diversity of hydraulic traits and potential mechanisms causing large-scale drought-induced mortality recently observed in several ecosystems.

Meteorological Influences on the Seasonality of Lyme Disease in the United States

Lyme disease (Borrelia burgdorferi infection) is the most common vector-transmitted disease in the United States. The majority of human Lyme disease (LD) cases occur in the summer months, but the timing of the peak occurrence varies geographically and from year to year. We calculated the beginning, peak, end, and duration of the main LD season in 12 highly endemic states from 1992 to 2007 and then examined the association between the timing of these seasonal variables and several meteorological variables. An earlier beginning to the LD season was positively associated with higher cumulative growing degree days through Week 20, lower cumulative precipitation, a lower saturation deficit, and proximity to the Atlantic coast. The timing of the peak and duration of the LD season were also associated with cumulative growing degree days, saturation deficit, and cumulative precipitation, but no meteorological predictors adequately explained the timing of the end of the LD season.

Dynamics of cold acclimation and complex phytohormone responses in Triticum monococcum lines G3116 and DV92 differing in vernalization and frost tolerance level

Cold stress response was compared in the crowns, leaves, and roots of Triticum monococcum DV92 spring line and G3116 winter line. The cold exposure was associated with a rapid increase of water saturation deficit, which resulted in a strong up-regulation of abscisic acid. Simultaneously, other stress hormones: salicylic acid, aminocyclopropane carboxylic acid (precursor of ethylene), and jasmonic acid decreased. The stress application resulted in a decrease of hormones associated with stimulation of cell growth and division (gibberellins, cytokinins, and auxin). During the acclimation phase of the stress response, the plants increased their frost tolerance and started the accumulation of dehydrins. Active gibberellin, cytokinins, and auxin were elevated; more rapidly in the spring line. Abscisic acid decrease was accompanied by a gradual increase of the other stress hormones. Simultaneously, the up-regulation of phenolic acids was observed, including ferulic and sinapic acids, which may be involved in the stabilization of auxin levels as well as antioxidative functions. After 21 days, the spring line DV92 exhibited its maximum of active cytokinins, which indicates the onset of the early stage of reproductive development. The winter line fulfilled its vernalization requirement after 42 days, as indicated by a decrease of frost tolerance and dehydrin levels, accompanied by similar growth hormone changes as in DV92. The similarities and differences between einkorn and common wheat in a long-term cold response are discussed.

Effects of Detrital Inputs and Roots on Carbon Saturation Deficit of a Temperate Forest Soil

Soil C sequestration has been proposed as a tool for addressing climate change. However, models used to predict soil C sequestration do not account for C saturation and functional differences among soil C pools. In this study, we examined differences in soil C pool content of a forest soil in Pennsylvania following 20 yr of detrital manipulation (i.e., control, no roots, no leaf litter, no inputs, double leaf litter). Detrital input treatments had a highly significant (ANOVA, F = 10.6, p < 0.0001) effect on soil C in the 0‐ to 5‐cm soil depth. However, soil C pools responded differently to the different treatments: the intra‐microaggregate silt + clay, intra‐microaggregate particulate organic matter (POM), and silt + clay within large macroaggregates in plots receiving no detrital inputs had significantly lower C concentrations (1.1, 2.5, and 0.4 g C kg−1 soil, respectively) than the control, double‐leaf‐litter, and no‐roots plots. Carbon in coarse POM within small macroaggregates was significantly lower in double‐leaf‐litter (4.5 g C kg−1 soil) and no‐leaf‐litter plots (6.6 g C kg−1 soil) than all other treatments (15.3–28 g C kg−1 soil). The intra‐microaggregate fractions in double‐leaf‐litter plots had greater C concentrations than in the control plots; along with moderate C concentrations in all bulk soil samples, this suggests that the soil is not yet approaching C saturation. This study reinforces the use of microaggregates within large macroaggregates as a diagnostic fraction for changes in soil C content and demonstrates that altering the organic matter source and quantity significantly affects soil C sequestration dynamics. Consideration of these factors will enable improved assessment of soil C sequestration capacity and management.

Physiological and Yield Performance of Chickpea Genotypes under Drought Stress

Ten high yielding chickpea genotypes were evaluated for yield performance under drought stress (rainfed) and non-stress (irrigated) conditions revealed the existence of considerable genetic variability in experimental materials. The magnitude of phenotypic coefficient of variation (PCV) was higher than genotypic coefficient of variation (GCV) for most of the characters. Relative water content (RWC) at pod development had high direct effect on seed yield under drought stress and non-stress conditions, while, direct effect of water saturation deficit (WSD) at pod development, showed negative impact on seed yield. Genotype IG 370 showed earliness in flowering and maturity under both drought stress and non-stress conditions and gave better yield (1674 kg/ha) with better drought tolerance efficiency as compared to late maturing genotypes (IG 226, KAK 2 and IG 592). Other genotypes namely, Vishal, IG 592, JG 412 and Ujjain 21 exhibited comparatively lower reduction in yield due to drought stress and high drought tolerance efficiency.

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF LYCHEE (LITCHI CHINENSIS SONN.): A REVIEW

SUMMARYThe results of research into the water relations and irrigation requirements of lychee are collated and reviewed. The stages of plant development are summarised, with an emphasis on factors influencing the flowering process. This is followed by reviews of plant water relations, water requirements, water productivity and, finally, irrigation systems. The lychee tree is native to the rainforests of southern China and northern Vietnam, and the main centres of production remain close to this area. In contrast, much of the research on the water relations of this crop has been conducted in South Africa, Australia and Israel where the tree is relatively new. Vegetative growth occurs in a series of flushes. Terminal inflorescences are borne on current shoot growth under cool (<15 °C), dry conditions. Trees generally do not produce fruit in the tropics at altitudes below 300 m. Poor and erratic flowering results in low and irregular fruit yields. Drought can enhance flowering in locations with dry winters. Roots can extract water from depths greater than 2 m. Diurnal trends in stomatal conductance closely match those of leaf water status. Both variables mirror changes in the saturation deficit of the air. Very little research on crop water requirements has been reported. Crop responses to irrigation are complex. In areas with low rainfall after harvest, a moderate water deficit before floral initiation can increase flowering and yield. In contrast, fruit set and yield can be reduced by a severe water deficit after flowering, and the risk of fruit splitting increased. Water productivity has not been quantified. Supplementary irrigation in South-east Asia is limited by topography and competition for water from the summer rice crop, but irrigation is practised in Israel, South Africa, Australia and some other places. Research is needed to determine the benefits of irrigation in different growing areas.

Spatiotemporal variations of reference evapotranspiration in recent five decades in the arid land of Northwestern China

Spatial and temporal variations of reference evapotranspiration (ET0) are useful for regional agricultural and water resources management as well as required in most distributed hydrological modelling. In the current study, the Penman–Monteith estimated ET0 in the arid land of Northwestern China has been explicitly explored using the Mann–Kendall test. Most stations in the study region exhibited significant decreasing trend of ET0 (P < 0.05) with only few occasions showing significant increasing trend (P < 0.05), despite the increase of temperature in the entire region. Analysis results revealed that the overall decreasing wind speed contributed most to the decreasing trend of ET0, whereas the contributions of relative humidity and sunshine duration were limited. Temperature played the second important role on determining ET0 trend, but its effect was opposite to that of wind speed and was largely offset by the decreasing wind speed. Furthermore, sensitivity analysis suggested the impact of temperature to ET0 was much larger than formerly reported if its effect on saturated vapour deficit was taken into account. The results obtained in the current study will help for better understanding of the effects of climate changes to water resource management in the arid land of northwest China. Copyright © 2013 John Wiley & Sons, Ltd.

Carbon sequestration potential of soils in southeast Germany derived from stable soil organic carbon saturation

Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global CO2 mitigation. However, the potential of soils to sequester soil organic carbon (SOC) in a stable form, which is limited by the stabilization of SOC against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential SOC saturation of silt and clay particles according to Hassink [Plant and Soil 191 (1997) 77] on the basis of 516 soil profiles. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long-term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse-textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395Mt CO2 -equivalents could theoretically be stored in A horizons of cultivated soils - four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to CO2 mitigation. Moreover, increasing SOC stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.

Atlantic Hurricanes and Climate Change. Part II: Role of Thermodynamic Changes in Decreased Hurricane Frequency

Abstract A method of downscaling that isolates the effect of temperature and moisture changes on tropical cyclone (TC) activity was presented in Part I of this study. By applying thermodynamic modifications to analyzed initial and boundary conditions from past TC seasons, initial disturbances and the strength of synoptic-scale vertical wind shear are preserved in future simulations. This experimental design allows comparison of TC genesis events in the same synoptic setting, but in current and future thermodynamic environments. Simulations of both an active (September 2005) and inactive (September 2009) portion of past hurricane seasons are presented. An ensemble of high-resolution simulations projects reductions in ensemble-average TC counts between 18% and 24%, consistent with previous studies. Robust decreases in TC and hurricane counts are simulated with 18- and 6-km grid lengths, for both active and inactive periods. Physical processes responsible for reduced activity are examined through comparison of monthly and spatially averaged genesis-relevant parameters, as well as case studies of development of corresponding initial disturbances in current and future thermodynamic conditions. These case studies show that reductions in TC counts are due to the presence of incipient disturbances in marginal moisture environments, where increases in the moist entropy saturation deficits in future conditions preclude genesis for some disturbances. Increased convective inhibition and reduced vertical velocity are also found in the future environment. It is concluded that a robust decrease in TC frequency can result from thermodynamic changes alone, without modification of vertical wind shear or the number of incipient disturbances.

Soil Organic Carbon Stock, Moisture Availability and Crop Yield as Influenced by Residue Management and Tillage Practices in Maize–Mustard Cropping System Under Hill Agro-Ecosystem

Residue management can notably influence crop production under any agro-climatic situation. A field experiment was conducted for three consecutive years (2005–2007) to evaluate various residue management and tillage practices on soil organic carbon (SOC), moisture conservation and crop productivity (maize: Zea mays L. and mustard: Brassica campestris L.) in a clay loam soil under hilly eco-system of northeast India. Six residue management combinations [M0—control, M1—Maize stalk cover (MSC), M2—MSC + Ambrosia sp. at 5 t ha−1, M3—MSC + Ambrosia sp. at 10 t ha−1, M4—MSC + poultry manure at 5 t ha−1 + Ambrosia sp. at 5 t ha−1 and M5—MSC + FYM at 10 t ha−1] were tested under conservation and conventional tillage. Results showed that all residue management practices significantly increased SOC density and SOC stock (with increases ranging from 40 to 165 %) relative to the control through incorporation of crop biomass and vegetation over the time period. Highest values were obtained with the M4 treatment (1385 g m−2 and 13.78 Mg ha−1, 1292 g m−2 and 12.94 Mg ha−1, respectively under conservation and conventional tillage practice). Conservation tillage had higher SOC (7.3 %) than conventional tillage practice. The soil moisture content measured at various soil depths revealed that it was consistently higher in residue management treatments, which is also reflected in relative leaf water content and water saturation deficit values. Higher moisture content prevailed under residue management practices at 15–30 cm soil depth, highest being in M4 treatment (33.14 %). All the residue management practices recorded higher crop yield, with increases ranging from 41 to 165 and 235 to 450 % for mustard in relation with control without residue. Among all the treatments, M4 recorded highest crop yield (mean value 2,503 kg ha−1 for maize and 2,418 kg ha−1 for mustard) than control (1,006 and 465 kg ha−1, respectively for maize and mustard). The study indicated that the integrated supply of MSC, poultry manure and Ambrosia sp. at 5 t ha−1 each under conservation tillage contributed most suitable soil physical environment for crop growth. However, a simple maize stock cover also resulted in significant effects on SOC, soil moisture and improved crop yield. Therefore, residue management should be adopted for support of double cropping in hill eco-system of north-east India.

An analysis of factors determining spatial variable grain yield of winter wheat

We analyzed under the temperate weather conditions of northwest Germany the relationships between soil water supply, crop canopy dynamics, radiation interception, components of the soil water balance and grain yield of winter wheat using data obtained from field experiments during three years. A dynamic model of the soil water budget in combination with frequent measurements of canopy parameters thereby was used to estimate the components of the water balance and radiation interception site specifically. Differences in soil texture and soil water supply characteristics in combination with variable canopy dynamics lead to substantial differences in radiation interception, components of the soil water budget and yield. The sum of intercepted photosynthetic active radiation corrected for drought stress by the ratio of actual to potential transpiration showed a unique positive correlation to grain yield over the three experimental years. Positive correlations between grain yield and actual transpiration normalized by saturation deficit were also found, however, the slopes differed between years. The best predictor of grain yield was the ratio of the sum actual transpiration to the sum of potential evapotranspiration. We could also show that drought stress corrected radiation interception and the ratio ΣTa/ΣETp evaluated at end of May already correlated significantly with final grain yield. This may offer options for improved site specific crop management.

A Novel Integrated Rainfall-Runoff Model Based on TOPMODEL and Artificial Neural Network

Conventional process-based rainfall-runoff models are difficult to catch the non-linear factors and to take full advantages of previous information of rainfall and runoff. However, these factors are closely related to the initial watershed average saturation deficit at each time step. Therefore, in order to address the issue, this study selected the parameter about initial underground flow in TOPMODEL (TOPOgraphic driven Model) as the breakthrough point. Then we used the previous two-day observed runoff and rainfall data as the inputs of an artificial neural network (ANN) and initial subsurface flow of present day as an output, then integrated ANN into runoff generation module in TOPMODEL and finally applied the integrated model for daily runoff modeling in Yingluoxia watershed with 10009km2, China. In addition, this work also utilized particle swarm optimization technique (PSO) to avoid the local optimization, especially for the integration of black-box and physical models. The result shows that during the validation period the Nash-Sutcliffe efficiency coefficient (NE) and root mean square error (RMSE) of TOPMODEL are 0.45 and 3.88×10-4m respectively while the NE of 0.70 and RMSE of 2.85×10-4m for the integrated model. Significantly, the integrated model performs much better than the traditional model. Hence, this new method of integrating ANN with the runoff generation module of TOPMODEL is promising and easily extended to other process-based rainfall-runoff models as well.

Using global maps to predict the risk of dengue in Europe

This article attempts to quantify the risk to Europe of dengue, following the arrival and spread there of one of dengue's vector species Aedes (Stegomyia) albopictus. A global risk map for dengue is presented, based on a global database of the occurrence of this disease, derived from electronic literature searches. Remotely sensed satellite data (from NASA's MODIS series), interpolated meteorological data, predicted distribution maps of dengue's two main vector species, Aedes aegypti and Aedes albopictus, a digital elevation surface and human population density data were all used as potential predictor variables in a non-linear discriminant analysis modelling framework. One hundred bootstrap models were produced by randomly sub-sampling three different training sets for dengue fever, severe dengue (i.e. dengue haemorrhagic fever, DHF) and all-dengue, and output predictions were averaged to produce a single global risk map for each type of dengue. This paper concentrates on the all-dengue models. Key predictor variables were various thermal data layers, including both day- and night-time Land Surface Temperature, human population density, and a variety of rainfall variables. The relative importance of each may be shown visually using rainbow files and quantitatively using a ranking system. Vegetation Index variables (a common proxy for humidity or saturation deficit) were rarely chosen in the models. The kappa index of agreement indicated an excellent (dengue haemorrhagic fever, Cohen's kappa=0.79±0.028, AUC=0.96±0.007) or good fit of the top ten models in each series to the data (Cohen's kappa=0.73±0.018, AUC=0.94±0.007 for dengue fever and 0.74±0.017, AUC=0.95±0.005 for all dengue). The global risk map predicts widespread dengue risk in SE Asia and India, in Central America and parts of coastal South America, but in relatively few regions of Africa. In many cases these are less extensive predictions than those of other published dengue risk maps and arise because of the key importance of high human population density for the all-dengue risk maps produced here. Three published dengue risk maps are compared using the Fleiss kappa index, and are shown to have only fair agreement globally (Fleiss kappa=0.377). Regionally the maps show greater (but still only moderate) agreement in SE Asia (Fleiss kappa=0.566), fair agreement in the Americas (Fleiss kappa=0.325) and only slight agreement in Africa (Fleiss kappa=0.095). The global dengue risk maps show that very few areas of rural Europe are presently suitable for dengue, but several major cities appear to be at some degree of risk, probably due to a combination of thermal conditions and high human population density, the top two variables in many models. Mahalanobis distance images were produced of Europe and the southern United States showing the distance in environmental rather than geographical space of each site from any site where dengue currently occurs. Parts of Europe are quite similar in Mahalanobis distance terms to parts of the southern United States, where dengue occurred in the recent past and which remain environmentally suitable for it. High standards of living rather than a changed environmental suitability keep dengue out of the USA. The threat of dengue to Europe at present is considered to be low but sufficiently uncertain to warrant monitoring in those areas of greatest predicted environmental suitability, especially in northern Italy and parts of Austria, Slovenia and Croatia, Bosnia and Herzegovina, Serbia and Montenegro, Albania, Greece, south-eastern France, Germany and Switzerland, and in smaller regions elsewhere.

A rainfall-runoff model parameterized from GIS and runoff data

A guiding principle in hydrological modelling should be to keep the number of calibration parameters to a minimum. A reduced number of parameters to be calibrated, while maintaining the accuracy and detail required by modern hydrological models, will reduce parameter and model structure uncertainty and improve model diagnostics. In this study, the dynamics of runoff are derived from the distribution of distances from points in the catchments to the nearest stream. This distribution is unique for each catchment and can be determined from a geographical information system. The distribution of distances, will, when a celerity of (subsurface) flow is introduced, provide a distribution of travel times, or a unit hydrograph (UH). For spatially varying levels of saturation deficit, we have different celerities and, hence, different UHs. Runoff is derived from the superposition of the different UHs. This study shows how celerities can be estimated if we assume that recession events represent the combined UHs for different levels of saturation deficit. A new soil moisture routine which estimates saturated and unsaturated volumes of subsurface water and with only one parameter to calibrate is included in the new model. The performance of the new model is compared with that of the Swedish HBV model and is found to perform equally well for eight Norwegian catchments although the number of parameters to be calibrated in the module concerning soil moisture and runoff dynamics is reduced from seven in the HBV model to one in the new model. It is also shown that the new model has a more realistic representation of the subsurface hydrology. Copyright © 2013 John Wiley & Sons, Ltd.