Velocity Mapping Toolbox (VMT): a processing and visualization suite for moving‐vessel ADCP measurements

The use of acoustic Doppler current profilers (ADCP) for discharge measurements and three‐dimensional flow mapping has increased rapidly in recent years and has been primarily driven by advances in acoustic technology and signal processing. Recent research has developed a variety of methods for processing data obtained from a range of ADCP deployments and this paper builds on this progress by describing new software for processing and visualizing ADCP data collected along transects in rivers or other bodies of water. The new utility, the Velocity Mapping Toolbox (VMT), allows rapid processing (vector rotation, projection, averaging and smoothing), visualization (planform and cross‐section vector and contouring), and analysis of a range of ADCP‐derived datasets. The paper documents the data processing routines in the toolbox and presents a set of diverse examples that demonstrate its capabilities. The toolbox is applicable to the analysis of ADCP data collected in a wide range of aquatic environments and is made available as open‐source code along with this publication. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Spatial variation of flow characteristics in a subarctic meandering river in ice-covered and open-channel conditions: A 2D hydrodynamic modelling approach

To be able to understand year-round river channel evolution both at present and in the future, the spatial variation of the flow characteristics and their sediment transport capabilities under ice cover need to be detected. As the measurements done through cross-sectional drill holes cover only a small portion of the river channel area, the numerical simulations give insight into the wider spatial horizontal variation of the flow characteristics. Therefore, we simulate the ice-covered flow with a hydrodynamic two-dimensional (2D) model in a meandering subarctic river (Pulmanki River, Finland) in mid-winter conditions and compare them to the pre-winter open-channel low flow situation. Based on the simulations, which are calibrated with reference measurements, we aim to detect (1) how ice-covered mid-winter flow characteristics vary spatially and (2) the erosion and sedimentation potential of the ice-covered flow compared to open-channel conditions. The 2D hydrodynamic model replicated the observed flow characteristics in both open-channel and ice-covered conditions. During both seasons, the greatest erosional forces locate in the shallow sections. The narrow, freely flowing channel area found in mid-winter cause the main differences in the spatial flow variation between seasons. Despite the causes of the horizontal recirculating flow structures being similar in both seasons, the structures formed in different locations depended on whether the river was open or ice covered. The critical thresholds for particle entrainment are exceeded more often in open-channel conditions than during ice-covered flow. The results indicate spatially extensive sediment transport in open-channel conditions, but that the spatial variability and differences in depositional and erosional locations increase in ice-covered conditions. Asymmetrical bends and straight reaches erode throughout the year, whereas symmetrical, smaller bends mainly erode in open-channel conditions and are prone to deposition in winter. The long ice-covered season can greatly affect the annual morphology of the submerged channel. © 2019 John Wiley & Sons, Ltd.     

乌梁素海冰封期湖泊冰盖组构特征对污染物分布的影响

为探究富营养化浅水湖泊季节性冰盖污染物分布规律,于2013-2014年冰封期,钻取乌梁素海湖泊冰盖冰芯试样,观测冰厚并对冰芯晶体结构、气泡含量、污染物浓度(总氮、总磷和COD_(Cr))进行分析.结果表明:冰盖可分为4层,中间2层冰晶体粒径较大且气泡含量较少,为冰盖热力生长区.冰盖以柱状晶体居多,粒径随深度增加而增加,气泡含量随冰盖密度增加而减少.冰盖结构特征与污染物分布具有相关关系,冰芯密度及气泡分布与总氮、总磷和COD_(Cr)相关关系分别为0.8965、0.8718、0.8184,并建立多元回归模型揭示冰封期湖泊水质特征,为季节性湖泊冰盖研究及冰封期湖泊水资源规划和管理提供理论依据.     

Influence of experimental removal of large woody debris on spatial patterns of three‐dimensional flow in a meander bend

This study reports the results of a large woody debris (LWD) removal experiment in a meander bend along a low‐energy stream in the Midwestern United States. The LWD obstacle was located in the center of the channel at the bend exit and consisted of a mature tree with an intact soil‐covered root wad and a large accumulation of logs, branches and pieces of lumber on top of and adjacent to the main tree. The results indicate that the LWD obstruction influenced 3D flow structure in this bend at all flow stages. The main effect of LWD is to dramatically decelerate flow throughout the majority of the bend, while locally accelerating flow where it passes through the narrow chute at the downstream end of the LWD obstruction. Results from the LWD removal experiment indicate that patterns of three‐dimensional flow structure in meander bends are sensitive to complete removal of LWD. After the removal of LWD from the bend, both downstream and secondary velocities increased and, though still weak, secondary flow intensified. Large, relatively stable, obstructions that span a significant portion of the channel may act as natural dams, effectively ponding water upstream of the LWD, thereby producing substantial convective deceleration of the flow. This research is the first to document three‐dimensional flow structure before and after a controlled removal of LWD from a meander bend. Studies of the type reported here represent a first step toward determining the ensemble of process interactions between LWD and bend dynamics. Copyright © 2006 John Wiley & Sons, Ltd.     

An experimental evaluation of ice cover effects on the dynamic behaviour of a concrete gravity dam

An extensive forced‐vibration testing programme has been carried out on an 84‐m concrete gravity dam located in northeastern Québec, Canada. The dam was subjected to a harmonic load on the crest in summer and severe winter conditions with temperatures ranging from ?10°C to ?15°C and a 1.0–1.5m ice cover. Acceleration and hydrodynamic frequency responses were obtained in different locations on the dam and in the reservoir. The main objective of the repeated tests was to investigate the effects of the ice cover on the dynamic behaviour of the dam–reservoir–foundation system, by comparing summer and winter results. Modifications in damping and resonance frequencies were observed, as well as an additional resonance that was attributed to an interaction of the dam with the ice cover. These findings provided a reliable and unique database for the investigations of dam–reservoir–foundation interaction and, in particular, the ice‐cover effects for dams located in northern regions. Copyright © 2002 John Wiley & Sons, Ltd.     

Modelling inter-annual and spatial variability of ice cover in a temperate lake with complex morphology

The formation of ice cover on lakes alters heat and energy transfer with the water column. The fraction of surface area covered by ice and the timing of ice-on and ice-off therefore affects hydrodynamics and the seasonal development of stratification and related ecosystem processes. Multi-year model simulations of temperate lake ecosystems that freeze partially or completely therefore require simulation of the formation and duration of ice cover. Here we present a multi-year hydrodynamic simulation of an alpine lake with complex morphology (Lower Lake Constance, LLC) using the three-dimensional (3D) model Aquatic Ecosystem Model (AEM3D) over a period of 9 years. LLC is subdivided into three basins (Gnadensee, Zeller See and Rheinsee) which differ in depth, morphological features, hydrodynamic conditions and ice cover phenology and thickness. Model results were validated with field observations and additional information on ice cover derived from a citizen science approach using information from social media. The model reproduced the occurrence of thin ice as well as its inter-annual variability and differentiated the frequency and extent of ice cover between the three sub-basins. It captured that full ice cover occurs almost each winter in Gnadensee, but only rarely in Zeller See and Rheinsee. The results indicate that the 3D model AEM3D is suitable for simulating long-term dynamics of thin ice cover in lakes with complex morphology and inter-annual changes in spatially heterogeneous ice cover.     

A distributed TOPMODEL for modelling impacts of land‐cover change on river flow in upland peatland catchments

There is global concern about headwater management and associated impacts on river flow. In many wet temperate zones peatlands can be found covering headwater catchments. In the UK there is major concern about how environmental change, driven by human interventions, has altered the surface cover of headwater blanket peatlands. However, the impact of such land‐cover changes on river flow is poorly understood. In particular, there is poor understanding of the impacts of different spatial configurations of bare peat or well‐vegetated, restored peat on river flow peaks in upland catchments. In this paper, a physically based, distributed and continuous catchment hydrological model was developed to explore such impacts. The original TOPMODEL, with its process representation being suitable for blanket peat catchments, was utilized as a prototype acting as the basis for the new model. The equations were downscaled from the catchment level to the cell level. The runoff produced by each cell is divided into subsurface flow and saturation‐excess overland flow before an overland flow calculation takes place. A new overland flow module with a set of detailed stochastic algorithms representing overland flow routing and re‐infiltration mechanisms was created to simulate saturation‐excess overland flow movement. The new model was tested in the Trout Beck catchment of the North Pennines of England and found to work well in this catchment. The influence of land cover on surface roughness could be explicitly represented in the model and the model was found to be sensitive to land cover. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of changing climate on ice cover in three morphometrically different lakes

A one‐dimensional hydrodynamic lake model (DYRESM‐WQ‐I) is employed to simulate ice cover and water temperatures over the period 1911–2014. The effects of climate changes (air temperature and wind speed) on ice cover (ice‐on, ice‐off, ice cover duration, and maximum ice thickness) are modeled and compared for the three different morphometry lakes: Fish Lake, Lake Wingra, and Lake Mendota, located in Madison, Wisconsin, USA. It is found that the ice cover period has decreased due to later ice‐on dates and earlier ice‐off dates, and the annual maximum ice cover thickness has decreased for the three lakes during the last century. Based upon simulated perturbations of daily mean air temperatures across the range of ?10°C to +10°C of historical values, Fish Lake has the most occurrences of no ice cover and Lake Wingra still remains ice covered under extreme conditions (+10°C). Overall, shallower lakes with larger surface areas appear more resilient to ice cover changes caused by climate changes.     

Hydro‐climatic impacts on the ice cover of the lower Peace River

Since the late 1960s, a paucity of ice‐jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the Peace–Athabasca Delta (PAD) region. Though major ice jams occur at breakup, antecedent conditions play a significant role in their frequency and severity. These conditions are partly defined by the mode of freezeup and the maximum thickness that is attained during the winter, shortly before the onset of spring and development of positive net heat fluxes to the ice cover. Data from hydrometric gauge records and from field surveys are utilized herein to study these conditions. It is shown that freezeup flows are considerably larger at the present time than before regulation, and may be responsible for more frequent formation of porous accumulation covers. Despite a concomitant rise in winter temperatures, solid‐ice thickness has increased since the 1960s. Using a simple ice growth model, specifically developed for the study area, it is shown that porous accumulation covers enhance winter ice growth via accelerated freezing into the porous accumulation. Coupled with a reduction in winter snowfall, this effect can not only negate, but reverse, the effect of warmer winters on ice thickness, thus explaining present conditions. The present model is also shown to be a useful prediction tool, especially for extrapolating incomplete data to the end of the winter. Copyright © 2007 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

Impact of flow variability on the morphology of a low-energy meandering river

Few studies have precisely documented the response of stream channels to short-term flow variability. This paper examines the impact of sequential flows of various magnitudes on the morphology of a low-energy river in northeastern Illinois, U.S.A. Between June 1986 and November 1988 channel cross-sections were surveyed on a semiannual basis at 26 locations along a 7.2 km stretch of the Des Plaines River. During this period an estimated 100-year flood, several bankfull flows, and an extreme low flow associated with a severe drought occurred. The response of the river channel to each of these events was relatively minor. Mean changes for the reach were generally less than 3 per cent for mean depth and less than 1 per cent for width. Statistical analysis indicates that net changes in width and depth over the entire period were not significantly different from zero. This lack of geomorphic response is attributable to low stream power, low hydrologic variability, fine bed materials, and cohesive banks along this stretch of river. Although dramatic changes in channel morphology did not occur, subtleties in geomorphic response were observed that reflect the temporal ordering of hydrologic events.     

Migration rate of river bends estimated by tree ring analysis for a meandering river in the source region of the Yellow River

Meandering rivers have dynamic evolution characteristics of lateral migration and longitudinal creeping movement, and studies on the migration rate of meandering rivers have both scientific and practical significance for understanding the evolution process. A river source region often is sparsely populated and lacks long-term monitoring data, making it difficult to estimate the migration rate of river bends. In the source region of the Yellow River, located in the northeastern part of the Qinghai-Tibet Plateau, China, meandering rivers have extensively developed. Combined with field investigation and sampling in the source region in 2016 and 2017, 9 river bends in the middle Baihe River were selected to attempt estimation of migration rates of the river bends using tree ring analysis. The tree core and disc samples were collected using an increment borer and a crosscut saw, and the ages of the trees were estimated based on tree ring analysis. A method for estimating the migration rate of river bends based on the relation between positions and ages of trees grown on the point bars in inner banks is proposed. The estimated migration rates of the 9 river bends of the Baihe River ranged 0.38–6.10 m/yr, and the migration rates were found to be related to the flow rate, channel slope, height of the outer bank, and width of the river valley. The maximum migration rate was determined to be at the No. 9 River Bend where the ratio of the meander-bend radius to the channel width (R/W) was 2.31, which is consistent with previous findings that the bend migration is most rapid in the ‘migration phase’. The proposed method for estimating the migration rate of river bends provides a potential alternative option for future study on the morphodynamic process of a meandering river.     

Mean and turbulent flow fields in a simulated ice‐covered channel with a gravel bed: some laboratory observations

Northern rivers experience freeze‐up over the winter, creating asymmetric under‐ice flows. Field and laboratory measurements of under‐ice flows typically exhibit flow asymmetry and its characteristics depend on the presence of roughness elements on the ice cover underside. In this study, flume experiments of flows under a simulated ice cover are presented. Open water conditions and simulated rough ice‐covered flows are discussed. Mean flow and turbulent flow statistics were obtained from an Acoustic Doppler Velocimeter (ADV) above a gravel‐bed surface. A central region of faster flow develops in the middle portion of the flow with the addition of a rough cover. The turbulent flow characteristics are unambiguously different when simulated ice covered conditions are used. Two distinct boundary layers (near the bed and in the vicinity of the ice cover, near the water surface) are clearly identified, each being characterized by high turbulent intensity levels. Detailed profile measurements of Reynolds stresses and turbulent kinetic energy indicate that the turbulence structure is strongly influenced by the presence of an ice cover and its roughness characteristics. In general, for y/d > 0·4 (where y is height above bed and d is local flow depth), the addition of cover and its roughening tends to generate higher turbulent kinetic energy values in comparison to open water flows and Reynolds stresses become increasingly negative due to increased turbulence levels in the vicinity of the rough ice cover. The high negative Reynolds stresses not only indicate high turbulence levels created by the rough ice cover but also coherent flow structures where quadrants one and three dominate. Copyright © 2012 John Wiley & Sons, Ltd.     

Time-averaged flow structure in the central region of a stream confluence

Previous process-oriented field studies of stream confluences have focused mainly on fluvial dynamics at or immediately downstream of the location where the confluent flows enter the downstream channel. This study examines in detail the spatial evolution of the time-averaged downstream velocity, cross-stream velocity, and temperature fields between the junction apex, where the flows initially meet, and the entrance to the downstream channel. A well-defined, vertically oriented mixing interface exists within this portion of the confluence, suggesting that lateral mixing of the incoming flows is limited. The downstream velocity field near the junction apex is characterized by two high-velocity cores separated by an intervening region of low-velocity or recirculating fluid. In the downstream direction, the high-velocity cores move inwards towards the mixing interface and high-velocity fluid progressively extends downwards into a zone of scour, resulting in an increase in flow velocity in the centre of the confluence. The cross-stream velocity field is dominated by flow convergence, but also includes a component associated with a consistent pattern of secondary circulation. This pattern is characterized by two surface-convergent helical cells, one on each side of the mixing interface. The helical cells appear to be the mechanism by which high-momentum fluid near the surface is advected downwards into the zone of scour. For transport-ineffective flows, the dimensions and intensities of the cells are controlled by the momentum ratio of the confluent streams and by the extant bed morphology within the confluence. Although the flow structure of formative events was not measured directly in this study, documented patterns of erosion and deposition within the central region of the confluence suggest that these events are dynamically similar to the measured flows, except for the fact that formative flows are not constrained by, but can reshape, the bed morphology. The results of this investigation are consistent with and augment previous findings on time-averaged flow structure in the downstream portion of the confluence. © 1998 John Wiley & Sons, Ltd.     

River flow regime and snow cover of the Pamir Alay (Central Asia) in a changing climate

Abstract

The Vakhsh and Pyandj rivers, main tributaries of the Amu Darya River in the mountainous region of the Pamir Alay, play an important role in the water resources of the Aral Sea basin (Central Asia). In this region, the glaciers and snow cover significantly influence the water cycle and flow regime, which could be strongly modified by climate change. The present study, part of a project funded by the European Commission, analyses the hydrological situation in six benchmark basins covering areas of between 1800 and 8400 km², essentially located in Tajikistan, with a variety of topographical situations, precipitation amounts and glacierized areas. Four types of parameter are discussed: temperature, glaciation, snow cover and river flows. The study is based mainly on a long-time series that ended in the 1990s (with the collapse of the Soviet Union) and on field observations and data collection. In addition, a short, more recent period (May 2000 to May 2002) was examined to better understand the role of snow cover, using scarce monitored data and satellite information. The results confirm the overall homogeneous trend of temperature increase in the mountain range and its impacts on the surface water regime. Concerning the snow cover, significant differences are noted in the location, elevation, orientation and morphology of snow cover in the respective basins. The changes in the river flow regime are regulated by the combination of the snow cover dynamics and the increasing trend of the air temperature.

Editor Z.W. Kundzewicz     

Laboratory frost sorting by needle ice: a pilot experiment on the effects of stone size and extent of surface stone cover

Sorted patterned ground is ubiquitous where gravelly fine soil experiences freeze–thaw cycles, but experimental studies have rarely been successful in reproducing such patterns. This article reports an attempt to reproduce miniature sorted patterns by repeating needle‐ice formation, which simulates frost sorting in regions dominated by diurnal freeze–thaw cycles. Six full‐scale laboratory models were tested. They consisted of near‐saturated volcanic fine soil topped by small stones of uniform size; the models explored a range of stone size (~6, ~12, ~17 and ~22 mm) and surface abundance (20, 40 and 60% cover). The stones were placed in a grid on the surface. These models were subjected to 20–30 temperature excursions between 10 °C and ?5 °C in 12 hours. The evolution of surface patterns were visually traced by photogrammetry. A data logging system continuously monitored vertical soil displacements, soil temperatures and moistures at different depths. All experimental runs displayed needle‐ice formation (2–3 cm in height) and resulting displacement of stones. The soil domains tended to heave faster and higher than the stones, leading to outward movement of the former and concentration of the stones. In plan view, smaller stones showed relatively fast and long‐lasting movements, while larger stones stabilized after the first five cycles. The 20% stone cover produced stone islands, whereas the 40% cover resulted in sorted labyrinths (a circle‐island complex) that may represent incipient sorted circles. The average diameter or spacing of these forms are 12–13 cm, being comparable to those in the field. The experiments imply that needle‐ice activity promotes rapid formation of sorted patterns, although the formation of well‐defined sorted circles may require hundreds of diurnal frost heave cycles. Copyright © 2014 John Wiley & Sons, Ltd.     

The influence of macrophyte growth,typical of eutrophic conditions,on river flow velocities and turbulence production

The influence of emergent and submerged macrophytes on flow velocity and turbulence production is demonstrated in a 140 m reach of the River Blackwater in Farnborough, Hampshire, UK. Macrophyte growth occurs in patches and is dominated by Sparganium erectum and Sparganium emersum. In May 2001, patches of S. erectum were already established and occupied 18% of the channel area. The flow adjusted to these (predominantly lateral) patches by being channelled through a narrower cross‐section. The measured velocity profiles showed a logarithmic form, with deviations attributable to topographic control. The channel bed was the main source of turbulence. In September 2001, in‐stream macrophytes occupied 27% of the channel, and overhanging bank vegetation affected 32% of the area. Overall flow resistance, described by Manning's n, showed a threefold increase that could be attributed to the growth of S. emersum in the middle of the channel. Velocity profiles showed different characteristic forms depending on their position relative to plant stems and leaves. The overall velocity field had a three‐dimensional structure. Turbulence intensities were generally higher and turbulence profiles tended to mirror the velocity profiles. Evidence for the generation of coherent eddies was provided by ratios of the root mean square velocities. Spectral analysis identified deviations from the Kolmogorov ?5/3 power law and provided statistical evidence for a spectral short‐cut, indicative of additional turbulence production. This was most marked for the submerged vegetation and, in some instances, the overhanging bank vegetation. The long strap‐like leaves of S. emersum being aligned approximately parallel to the flow and the highly variable velocity field created by the patch arrangement of macrophytes suggest that the dominant mechanism for turbulence production is vortex shedding along shear zones. Wake production around individual stems of S. emersum close to the bed may also be important locally. Copyright © 2006 John Wiley & Sons, Ltd.     

Effects of helical flow in one‐dimensional modelling of sediment distribution at river bifurcations

Complex flow processes at river bifurcations and the influence of the layout of a bifurcation make it difficult to predict sediment distribution over the downstream branches in case bedload transport dominates. In one‐dimensional models we need a nodal point relationship that prescribes the distribution of sediment over the downstream branches. We have identified which factors need to be included in such a relationship for the division of bedload transport at bifurcations. Next, irrotational flow theory for idealized geometries has been used to derive a simple physics‐based nodal point relationship that accounts for the effects of helical flow in the situation that a channel takes off under an angle from a straight main channel. This first step towards a complete nodal point relationship is applicable to bedload transport situations if the flow is clearly curved and if there is no pronounced bed topography. The relationship has been tested against data from a unique set of laboratory measurements, numerical data and data from a scale model of the Rhine bifurcation at Pannerden in the Netherlands. We find that the derived model yields a reasonable prediction of the sediment division over the downstream branches, and yields better predictions than the Wang et al. model for the situation considered. Considering the relative complexity and limited accuracy of the nodal point relationship for the effect of helical flow alone, however, we conclude thatderiving a practical physics‐based 1‐D relationship including all relevant processes is not feasible. We therefore recommend 2‐D or 3‐D modelling for all cases in general where morphological evolution depends on the division of bedload transport at bifurcations. Copyright © 2012 John Wiley & Sons, Ltd.     

Experimental analysis of cross‐sectional flow motion in a large amplitude meandering bend

Flow in meandering bends is characterized by the formation of a large cross‐sectional central‐region circulation cell. The width‐to‐depth ratio is one of the most important parameters affecting the entity of the cross‐circulation motion. In steep outside bends, beside the central‐region cell, a counter‐rotating circulation cell often forms in the upper part of the outer‐bank. In spite of its practical importance, the evolving mechanisms of both the circulation cells and their role on boundary shear stress distribution in bends are not yet fully understood. The aim of the present paper is to gain some insight into how cross‐sectional flow motion evolves along meandering bends. Experiments have been carried out in a laboratory meandering channel of large amplitude, over a deformed‐rigid bed, for two values of the width‐to‐depth ratio. The three‐dimensional flow velocity field has been measured in detail at five cross‐sections, almost equally spaced along the channel reach between two consecutive apex sections. The measurements have been carried out on a fine grid by an acoustic Doppler velocity profiler. The distributions of the cross‐sectional flow (e.g. cross‐sectional flow velocity, net transversal flux) and turbulent kinetic energy are analyzed in each investigated section. Measurements show that the counter‐rotating circulation cell is evident only in the case of ‘small’ width‐to‐depth ratio. Such circulation cell begins at the bend entrance and it is fully developed at the bend apex; then it decays. At the bend apex, the core of maximum velocity is found near the bed at about the separation between the central and the outer‐bank circulation cells. Moreover, the presence of the counter‐rotating circulation cell allows the bank shear stress to maintain low values in the outer‐side of the bend. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of land cover change on duration and severity of high and low flows

Land cover has been increasingly recognized as an important factor affecting hydrologic processes at the basin and regional level. Therefore, improved understanding of how land cover change affects hydrologic systems is needed for better management of water resources. The objective of this study is to investigate the effects of land cover change on the duration and severity of high and low flows by using the Soil Water Assessment Tool model, Bayesian model averaging and copulas. Two basins dominated by different land cover in the Ohio River basin are used as study area in this study. Two historic land covers from the 1950s and 1990s are considered as input to the Soil Water Assessment Tool model, thereby investigating the hydrologic high and low flow response of different land cover conditions of these two basins. The relationships between the duration and severity of both low and high flow are defined by applying the copula method; changes in the frequency of the duration and severity are investigated. The results show that land cover changes affect both the duration and severity of both high and low flows. An increase in forest area leads to a decrease in the duration and severity during both high and low flows, but its impact is highest during extreme flows. The results also show that the land cover changes have had significant influences on changes in the joint return periods of duration and severity of low and high flows. While this study sheds light on the role of land cover change on severity and duration of high and low flow conditions, more studies using various land cover conditions and climate types are required in order to draw more reliable conclusions in the future. Copyright © 2016 John Wiley & Sons, Ltd.