Rainless Periods Research Articles

Analyzing cloud base at local and regional scales to understand tropical montane cloud forest vulnerability to climate change

Abstract. The degree to which cloud immersion provides water in addition to rainfall, suppresses transpiration, and sustains tropical montane cloud forests (TMCFs) during rainless periods is not well understood. Climate and land use changes represent a threat to these forests if cloud base altitude rises as a result of regional warming or deforestation. To establish a baseline for quantifying future changes in cloud base, we installed a ceilometer at 100 m altitude in the forest upwind of the TMCF that occupies an altitude range from ∼ 600 m to the peaks at 1100 m in the Luquillo Mountains of eastern Puerto Rico. Airport Automated Surface Observing System (ASOS) ceilometer data, radiosonde data, and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite data were obtained to investigate seasonal cloud base dynamics, altitude of the trade-wind inversion (TWI), and typical cloud thickness for the surrounding Caribbean region. Cloud base is rarely quantified near mountains, so these results represent a first look at seasonal and diurnal cloud base dynamics for the TMCF. From May 2013 to August 2016, cloud base was lowest during the midsummer dry season, and cloud bases were lower than the mountaintops as often in the winter dry season as in the wet seasons. The lowest cloud bases most frequently occurred at higher elevation than 600 m, from 740 to 964 m. The Luquillo forest low cloud base altitudes were higher than six other sites in the Caribbean by ∼ 200–600 m, highlighting the importance of site selection to measure topographic influence on cloud height. Proximity to the oceanic cloud system where shallow cumulus clouds are seasonally invariant in altitude and cover, along with local trade-wind orographic lifting and cloud formation, may explain the dry season low clouds. The results indicate that climate change threats to low-elevation TMCFs are not limited to the dry season; changes in synoptic-scale weather patterns that increase frequency of drought periods during the wet seasons (periods of higher cloud base) may also impact ecosystem health.

Transpiration of trees in a cool temperate forest on Mt. Aso, Japan: comparison of model simulation and measurements

AbstractIn the large caldera of Mt. Aso, Japan, artificial grasslands were converted into forests of different species due to the decline of the livestock industry in this region. These changes in species composition are thought to have changed not only the transpiration rates (E), but also the responses in E to variations in environmental conditions. For three introduced forest types, we monitored E using sap flux sensors and computed E with a multilayer model parameterized by independently obtained leaf‐scale ecophysiological traits. Modeled E replicated the time series of measured E reasonably well, but did not reproduce a decrease in E lasting 20 days after a short rainless period in conifer plantation. Mean leaf‐scale stomatal conductance of two deciduous broadleaved tree species was as low as that of trees under dry conditions in other studies, possibly an adaptation for the avoidance of excessive E during rainless periods. These results suggest that land use change influenced E and its response to the rainfall patterns of the region and that drought plays an important role in influencing species‐specific E characteristics in this rainy region. The multilayer model in combination with sap flux measurements was found to be a useful tool not only for the extrapolation of E, but also for the detection of the unexpected events, as long as the measured parameter values capture the species‐specific seasonality in leaf ecophysiological traits.

Georgian climate change under global warming conditions

Abstract Georgian Climate change has been considered comprehensively, taking into account World Meteorological Organization recommendations and recent observation data. On the basis of mean temperature and precipitation decadal trend geo-information maps for 1936–2012 years period, Georgian territory zoning has been carried out and for each areas climate indices main trends have been studied, that best characterize climate change - cold and hot days, tropical nights, vegetation period duration, diurnal maximum precipitation, maximum five-day total precipitation, precipitation intensity simple index, precipitation days number of at least 10 mm, 20 mm and 50 mm, rainy and rainless periods duration. Trends of temperature indices are statistically significant. On the Black Sea coastline and Colchis lowland at high confidence level cold and hot days and tropical nights number changes are statistically significant. On eastern Georgia plains at high level of statistical significance, the change of all considered temperature indices has been fixed except for the number of hot days. In mountainous areas only hot day number increasing is significant. Trends of most moisture indices are statistically insignificant. While keeping Georgian climate change current trends, precipitation amount on the Black Sea coastline and Colchis lowland, as well as in some parts of Western Caucasus to the end of the century will increase by 50% and amounts to 3000 and 6000 mm, respectively this will strengthen humidity of those areas. Besides increasing of rainy period duration may constitute the risk for flooding and high waters. On eastern Georgia plains, in particular Kvemo Kartli, annual precipitation amount will decrease by 50% or more, and will be only 150–200 mm and the precipitation daily maximum will decrease by about 20 mm and be only 10–15 mm, which of course will increase the intensity of desertification of steppe and semi-desert landscapes.

Geochemistry of trace elements in spring waters of the Lourdes area (France)

Geochemical studies on the waters of four springs, including the Massabielle (MS) Spring, were carried out at Lourdes (France) following a long, rainless and warm period, with the aim of at least documenting the groundwater chemistry that was affected by the current meteoric input. The existence of anecdotal reports about anomalously elevated concentrations of trace constituents in the water of the MS Spring in the absence of any detailed studies inspired these first geochemical investigations of trace elements in the spring waters at Lourdes. The main common features of waters from the four springs studied in Lourdes are low total dissolved solids (255–318 mg/L), a slightly alkaline pH (7.50–7.68), oxidizing conditions (E H = 458–472 mV), similar temperatures (11.3–13.1 °C), and their Ca-HCO 3 hydrochemical type, all of which are typical characteristics for an active zone within a hydrogeological system that is developed in carbonate-dominated bedrock. The spring waters, which represent an active turnover zone in the hydrogeological system, are only in partial chemical equilibrium with the minerals of the aquifer rocks. The enrichment of the MS Spring water with numerous elements (Li, Na, Cs, Ba, S, F, Br, REE, B, Sb and Bi), when compared with other springs studied and with the bedrock geochemistry, probably is caused by contributions from fluids (originating from the Pyrenees basement and/or from Triassic saliferous deposits) in the formation of the hydrogeochemical content of the zone under investigation. The germanium concentration in all of the waters studied was significantly lower than the concentrations typically found in fresh groundwater in the active zone; accordingly, the hypothesis concerning an anomalously high concentration of this element in the MS Spring water was invalidated. The preliminary geochemical research presented is part of an interdisciplinary geochemical-biological-tensiometric study of the spring waters at Lourdes.

Ammonia loss from urea in grassland and its mitigation by the new urease inhibitor 2-NPT

SUMMARYFollowing the surface application of granulated urea to grassland, high ammonia (NH3) losses of up to 30% have been reported. The addition of a urease inhibitor (UI) to urea granules could be a way to abate these losses. Field experiments were conducted at two intensive grassland sites in 2007 and 2008 to evaluate the potential of the new UI N-(2-nitrophenyl) phosphoric triamide (2-NPT; concentrations of 0·75, 1·0 and 1·5 g N/kg) to reduce NH3 emissions resulting from the application of granulated urea. Ammonia losses were continuously measured on plots fertilized with urea, urea + 2-NPT, calcium ammonium nitrate and a control (0N). The measurements were made with a dynamic chamber system. All measurement periods were started after a period of precipitation with a following rainless period being forecasted. Results over measurement periods of 10 days following fertilization are presented. Ammonia losses following the application of granulated urea varied between 4·6 and 11·8 kg N/ha, corresponding to 4·2 up to 14·0% of the applied nitrogen. The addition of 2-NPT to urea granules at three concentrations significantly reduced NH3 losses by 69–100%. Comparable losses of NH3 were observed for urea containing the UI 2-NPT as well as calcium ammonium nitrate, and were not significantly different from the control treatment. No relationships between losses, meteorological factors and soil moisture were observed. The addition of the UI 2-NPT to urea granules applied on grassland effectively reduced NH3 losses.

Assessment of Summer Drought in 2015 Using Different Indices in the Catchment of Blanice River

The year 2015 was characterized by a very low precipitation totals and long rainless periods all over the Czech Republic as well as other central European countries. This fact has attracted the attention of both the public as well as professional society whose focus was recently put more on floods which are hydrologic extremes with more sound impacts. In this paper, the summer period 2015 is in the focus for the catchment of Blanice River (Central Bohemia Region, South Bohemia Region). It was analyzed from both the meteorological and hydrological point of view. Total area of the catchment is 534 km2 and is located 50km southeast of Prague. For the assessment of drought, the data from one hydrological gauging as well as from a number of meteorological stations were used. The time series used for this study are more than 50 years long. Drought indices used for this study and presented in this paper were Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI) and deficit volumes (DV). The analyses of precipitation data carried out for given purpose were supported by GIS application in order to get real precipitation data based on available station data. Drought indexes were calculated on the basis of data for entire period, however the emphasis was put on the data from year 2015. The results of all performed analyses show the significance of the drought event which occurred in summer 2015 with respect to both meteorological and hydrological indices. However, the significance of meteorological drought seems to be higher with respect to the results of analyses carried out. The results also show, that there were even more severe drought episodes in past within the analyzed period.

Groundwater in the Earth's critical zone: Relevance to large‐scale patterns and processes

AbstractAlthough we have an intuitive understanding of the behavior and functions of groundwater in the Earth's critical zone at the scales of a column (atmosphere‐plant‐soil‐bedrock), along a toposequence (ridge to valley), and across a small catchment (up to third‐order streams), this paper attempts to assess the relevance of groundwater to understanding large‐scale patterns and processes such as represented in global climate and Earth system models. Through observation syntheses and conceptual models, evidence are presented that groundwater influence is globally prevalent, it forms an environmental gradient not fully captured by the climate, and it can profoundly shape critical zone evolution at continental to global scales. Four examples are used to illustrate these ideas: (1) groundwater as a water source for plants in rainless periods, (2) water table depth as a driver of plant rooting depth, (3) the accessibility of groundwater as an ecological niche separator, and (4) groundwater as the lower boundary of land drainage and a global driver of wetlands. The implications to understanding past and future global environmental change are briefly discussed, as well as critical discipline, scale, and data gaps that must be bridged in order for us to translate what we learn in the field at column, hillslope and catchment scales, to what we must predict at regional, continental, and global scales.

Intra‐event intermittency of rainfall: an analysis of the metrics of rain and no‐rain periods

AbstractThe metric or ‘observable’ properties of intra‐event rainfall intermittency (IERI) are quantified using a 10‐year record from arid Fowlers Gap, Australia. Rainfall events were delineated using the minimum inter‐event time (MIT) criterion, using eight values in the range of 1 h – 24 h. Within events, no‐rain periods were defined as corresponding to rainfall rates R < 0.1 mm/h or R < 0.2 mm/h (both less than typical wet‐canopy evaporation rates during rainfall). In this way, rainfall events were subdivided into rain and no‐rain periods. Intermittency was characterised using two measures: the fraction of rainless time within an event, and the duration of the longest rainless period. Events identified using a minimum inter‐event time (MIT) of 24 h included on average 9.4 h of contiguous no‐rain time (47.5% of the mean event duration), and only 6.8 h of contiguous rain. Total IERI averaged 51.1% for these events. Events defined with MIT = 6 h (a value commonly adopted in the literature) exhibited a mean of 1.53 h of no‐rain and 9.04 h of contiguous rain. Total IERI averaged 13.9% for these events for R < 0.1 mm/h, but reached 39.2% if no‐rain periods were taken as those of <0.2 mm/h. The maximum contiguous no‐rain period for events defined using MIT = 6 h was 10.9 h from an event of 12.6 h duration, and this represents 86.5% of the event duration. Results demonstrate that smaller, shorter, and less intense rainfall events tend to exhibit higher IERI than larger, longer, and more intense events. IERI is relevant to the understanding of land surface processes. Information on the metric properties of IERI in different rainfall types (convective and stratiform) and rainfall climates (arid, maritime, and wet tropical) may prove to have significance for diverse studies in land surface hydrology. Copyright © 2015 John Wiley & Sons, Ltd.

The role of condensation in the evolution of dissolutional forms in gypsum caves: Study case in the karst of Sorbas (SE Spain)

The karst of Sorbas (SE Spain) is one of the most important gypsum areas worldwide. Its underground karst network comprises over 100km of cave passages. Rounded smooth forms, condensation cupola and pendant-like features appear on the ceiling of the shallower passages as a result of gypsum dissolution by condensation water. Meanwhile, gypsum speleothems formed by capillarity, evaporation and aerosol deposition such as coralloids, gypsum crusts and rims are frequently observed closer to the passage floors. The role of condensation–dissolution mechanisms in the evolution of geomorphological features observed in the upper cave levels has been studied by means of long-term micro-erosion meter (MEM) measurements, direct collection and analysis of condensation waters, and micrometeorological monitoring. Monitoring of erosion at different heights on gypsum walls of the Cueva del Agua reveals that the gypsum surface retreated up to 0.033mmyr−1 in MEM stations located in the higher parts of the cave walls. The surface retreat was negligible at the lowest sites, suggesting higher dissolution rates close to the cave ceiling, where warmer and moister air flows. Monitoring of microclimatic parameters and direct measurements of condensation water were performed in the Covadura Cave system in order to estimate seasonal patterns of condensation. Direct measurements of condensation water dripping from a metal plate placed in the central part of the El Bosque Gallery of Covadura Cave indicate that condensation takes place mainly between July and November in coincidence with rainless periods. The estimated gypsum surface lowering due to this condensation water is 0.0026mmyr−1. Microclimatic monitoring in the same area shows differences in air temperature and humidity of the lower parts of the galleries (colder and drier) with respect to the cave ceiling (warmer and wetter). This thermal sedimentation controls the intensity of the condensation–evaporation mechanisms at different heights in the cave.

A novel conceptual framework for long‐term leaching of autochthonous soil particles during transient flow

SummaryTo date, most of the experimental and modelling research on the mobilization mechanisms of autochthonous colloidal‐sized soil particles has focused on single rainfall events. However, in the field, natural events interrupted by rainless periods of various durations follow one another. Some studies have shown that the amount of leached particles is much affected by the chronology of rainfall events. In this paper, we propose a model to compute the amount of mobilized particles during the transient flow regime of long series of successive rainfall events. Particles that can be mobilized are assumed to be located at the surface of preferential flow paths in contact with flowing water. As water passes, particles are mobilized, thus uncovering new particles and renewing the stock of mobilizable particles. We also report experimental data on the impact of long series of rainfall events on particle mobilization in undisturbed calcareous soil columns under controlled conditions. The model provides a framework to understand the variation of mobilization observed during the transient flow regime of these rainfall events. These variations resulted in part from the interplay between macropore water content at the onset of rain and the chronology of previous rainfall events. Additionally, the model provides a feedback loop between particle mobilization and minute macropore structure modifications. Once coupled with a particle transport model this feature may be useful to model soil structure changes during long series of successive rainfall events.

Rift Valley Fever outbreaks in Mauritania and related environmental conditions.

Four large outbreaks of Rift Valley Fever (RVF) occurred in Mauritania in 1998, 2003, 2010 and 2012 which caused lots of animal and several human deaths. We investigated rainfall and vegetation conditions that might have impacted on RVF transmission over the affected regions. Our results corroborate that RVF transmission generally occurs during the months of September and October in Mauritania, similarly to Senegal. The four outbreaks were preceded by a rainless period lasting at least a week followed by heavy precipitation that took place during the second half of the rainy season. First human infections were generally reported three to five weeks later. By bridging the gap between meteorological forecasting centers and veterinary services, an early warning system might be developed in Senegal and Mauritania to warn decision makers and health services about the upcoming RVF risk.

Performance Reduction of PV Systems by Dust Deposition

The deposition of dust on photovoltaic modules is of importance as parameter for economic analysis and life cycle assessments to evaluate this kind of technology for generation of electricity. Even though during the last two decades several photovoltaic plants were implemented, only a few studies about this issue were performed. This work tries to estimate the annual loss of generated energy caused by dust deposition on PV modules based on an experimental setup of a grid connected PV plant, monitoring of solar irradiation, onsite determination of dust deposition rate, and processing climatic data to obtain information about the frequency of rainfall occurrence. In Mexico City, air pollution with suspended particulate matter with diameter below 10μm (PM 10) is almost permanently over 50 μg m-3. This contamination contributed to an average dust deposition rate of 65 g m-2d-1 on horizontal surfaces. Dust accumulation during rainless periods of more than 60 days can reduce production of PV systems up to 15%. With the capacity of natural cleaning by rainfalls, annual loss of production is estimated to be 3.6%.

Effect of Water Table Depth on Growth and Yield of Soybean Yudou 16

AbstractIn 2005–2006, a multilysimeter study was conducted to determine the effect of various water table depths (WTDs) (0.2, 0.4, 0.6, 0.8, 1.0, 2.0, 3.0, 4.0, and 5.0 m) on the growth of soybean variety Yudou 16 in the transitional zone of northern semitropical and warm temperate climatic conditions of the Huaibei Plain, Anhui Province, China. In the experiment, precipitation was accounted for and WTD was controlled. The yield of Yudou 16 soybeans was greatest with a WTD of 2 m; yield decreased when the WTD was deeper or shallower than 2 m. From 0.2 through 2.0 m soybean yield increased rapidly with increasing WTD because shallow WTDs produced an oversupply of water in the root zone. From 2 through 5 m yield decreased slowly with increasing WTD under the experimental conditions. This was apparently because deeper WTDs could not compensate (through phreatic evaporation) for rainless periods of moisture stress during the growing season. When the constant WTD changes from 0.8 to 4.0 m, the yield is equal t...

Precipitation data considerations for evaluating subdaily changes in rainless periods due to climate change

Quantifying magnitudes and frequencies of rainless times between storms (TBS), or storm occurrence, is required for generating continuous sequences of precipitation for modeling inputs to small watershed models for conservation studies. Two parameters charac- terize TBS, minimum TBS (MTBS) and average TBS (ATBS)—both vary monthly and are calculated by assuming TBS follows an exponential distribution. Detecting changes in these parameters due to climate is important for precipitation and climate studies at short time and small spatial scales, but there are issues with depth resolution of precipitation data that must first be investigated. Precipitation data having one-minute temporal and 0.25 mm (0.01 in) depth resolutions from the UDSA Agricultural Research Service North Appalachian Experimental Watershed (NAEW) at Coshocton, Ohio, were used to determine the spatial variability and consistency of estimates over the 425 ha (1,050 ac) facility and the impacts of coarsening the depth resolution of data 10 times to 2.54 mm (0.1 in). The magnitudes and trends of changes in MTBS and ATBS are determined for three rain gauges over the NAEW and extended to other gauges in the Ohio region. Approximately 5,800 parameter pairs were computed for different data configurations. Small spatial scale, NAEW high-res- olution precipitation data shows consistent MTBS and ATBS long-term values for each month but more variability in estimates for MTBS than ATBS. Climate change trends for MTBS and ATBS are not apparent and generally consistent for different NAEW gauges, except for November when all gauges were consistently significant for ATBS. There is a weak indication that the fall months may be affected by significant shortening of ATBS at the NAEW and in northeastern Ohio due to climate change, but more data are needed. An imposed, coarser NAEW data resolution results in consistent no-trend indications for MTBS, but not for ATBS. The coarse-resolution data may not be adequate to characterize TBS for investigating changes due to climate change unless more data preparation is performed, such as identifying and excluding dry times when precipitation may have occurred. Precipitation records with mixed resolution data cannot be used to detect climate changes of dry periods. More data and data preparation are needed to arrive at firm conclusions regarding climate change effects on TBS in Ohio.

Spatial variability and interdependence of rain event characteristics in the Czech Republic

Rain event characteristics are assessed in a 10-year (1991–2000) record for 122 stations in the Czech Republic. Individual rain events are identified using the minimum interevent time (mit) concept. For each station, the optimal mit value is estimated by examining the distribution of interevent times. In addition, various mit values are considered to account for the effect of mit on rain event characteristics and their interrelationships. The interdependence between rain event characteristics and altitude, average rainfall depth, and geographic location are explored using simple linear models. Most rain event characteristics can be to some extent explained by average total rainfall or altitude, although models including the former significantly outperformed models using the latter. Significant correlation was found among several pairs of monthly mean characteristics often including event rain rate (with event duration, depth, maximum intensity, and fraction of intraevent rainless periods). Moreover, strong correlation was revealed between number of events, interevent time, event depth, and duration. In general, correlation decreases in absolute value with mit. Strong spatial correlation was found for the mean monthly interevent time and number of events. Spatial correlation was considerably smaller for other characteristics. In general, spatial dependence was smaller for larger mit values. Copyright © 2013 John Wiley & Sons, Ltd.

Production and Release of Asexual Sporangia in Plasmopara viticola

To study the influence of environmental conditions on sporulation of Plasmopara viticola lesions under vineyard's conditions, unsprayed vines were inspected every second or third day and the numbers of sporulating and nonsporulating lesions were counted in two North Italy vineyards in 2008 to 2010. Infected leaves were removed so that only fresh lesions were assessed at each field assessment. Sporulation was studied at two scales, across field assessments and across the seasonal population of lesions. Frequencies of sporulating lesions were positively correlated with the numbers of moist hours in the preceding dark period (i.e., the number of hours between 8:00 p.m. and 7:00 a.m. with relative humidity ≥80%, rainfall >0 mm, or wetness duration >30 min). In a receiver operating characteristic analysis, predicted sporulation based on the occurrence of ≥3 moist hours at night provided overall accuracy of 0.85. To study the time course of sporulation on lesions which were not washed by rainfall, numbers of sporangia produced per square millimeter of lesion were estimated on individual cohorts of lesions over the whole infectious period. The numbers of sporangia per square millimeter of lesion increased rapidly during the first 4 days after the beginning of sporulation and then tapered off prior to a halt; the time course of cumulative sporangia production by a lesion followed a monomolecular growth model (R(2) = 0.97). The total number of sporangia produced by a square millimeter of lesion increased as the maximum temperature decreased and moist hours in the dark increased. To study the release pattern of the sporangia, spore samplers were placed near grapevines with sporulating lesions. Airborne sporangia were caught in 91.2% of the days over a wide range of weather conditions, including rainless periods. The results of this study provide quantitative information on production of P. viticola sporangia that may help refine epidemiological models used as decision aids in grape disease management programs.

Evaporation modeling with multiple linear regression techniques– a review

Evaporation is influenced by number of agro-meteorological parameters and one of the integral components of the hydrological cycle and. Usually, estimates of evaporation are needed in a wide array of problems in agriculture, hydrology, agronomy, forestry and land resources planning, such as water balance computation, irrigation management, crop yield forecasting model, river flow forecasting, ecosystem modeling. Irrigation can substantially increase crop yields, but again the scheduling of the water application is usually based on evaporation estimates. Numerous investigators developed models for estimation of evaporation. The interrelated meteorological factors having a major influence on evaporation have been incorporated into various formulae for estimating evaporation. Unfortunately, reliable estimates of evaporation are extremely difficult to obtain because of complex interactions between the components of the land-plant-atmosphere system. In hot climate, the loss of water by evaporation from rivers, canals and open-water bodies is a vital factor as evaporation takes a significant portion of all water supplies. Even in humid areas, evaporation loss is significant, although the cumulative precipitation tends to mask it due to which it is ordinarily not recognized except during rainless period. Therefore, the need for reliable models for quantifying evaporation losses from increasingly scarce water resources is greater than ever before. Accurate estimation of evaporation is fundamental for effective management of water resources. The evaporation models using MLR techniques is discussed her in details.

Hydrological behavior of Alfisols and Vertisols in the semi-arid zone: Implications for soil and water management

Understanding of the hydrological behavior of soils is a prerequisite for developing appropriate soil and water management practices. Such information for Alfisols and Vertisols, the two major soils in the semi-arid tropics (SATs), is scanty especially from a long-term perspective. In this paper, we describe and discuss results from long-term (from 1976 to 2010) hydrological studies conducted on small agricultural watersheds on Vertisols and Alfisols at the ICRISAT Center, Patancheru, India. The hydrological behavior of soils are characterized in terms of runoff volume, peak runoff rate, number of runoff events, soil loss, sediment concentration and deep drainage loss under different rainfall, crop cover and soil moisture conditions to aid in developing effective soil and water management practices. We also provide details on the effects of annual and monthly rainfall on the hydrological behavior of these soils in different rainfall regions. The results show that Alfisols and Vertisols in the SATs have very contrasting hydrological behavior. Several findings emerging from our studies, are rather unexpected. For example, the sandy Alfisols with higher saturated hydrological conductivity generated higher runoff compared to the clayey Vertisols with extremely low saturated hydraulic conductivity. The undesirable early season runoff from Alfisols is higher than from Vertisols. The contribution of 1–2 big storms to annual runoff and soil loss was high on both soils. The contrasting hydrological behavior of these two soils is due to differences in soil characteristics such as crusting, sealing and low structural stability in Alfisols; and the presence of cracks during the early season and formation of micro-cracks during rainless periods in Vertisols. The results suggest that the information from the long-term hydrological studies is useful for determining appropriate soil and water management practices and strategies in different rainfall regions.

Implementation of conceptual linear storage model of runoff with diurnal fluctuation in rainless periods / Aplikace konceptuálního lineárního modelu základního odtoku s denní variabilitou v bezesrážkovém období, Česká republika. J. Hydrol. Hydromech., 60, 2012, 4; 27 lit., 8 obr., 3 tab.

The aim of this paper is to set up the model describing the depletion runoff process when a catchment is supplied only from subsurface water sources and also to describe a transpiration effect when depleted mostly by riparian vegetation considering it as a diurnal process in hot and rainless period. This model is conceived as a simple linear description of all forms of subsurface runoff supplying the stream flow in fully forested the Teply Brook small catchment (district Zdar nad Sazavou, the Czech Republic) for the dry seasons of 2003 to 2007 when the discharges were continuously recorded at the outlet. There are three interconnected soil water zones, represented by the corresponding subsurface storages in the model. Actual evapotranspiration from the riparian part of the catchment is approximated by a special form of the Fourier series. The model simulates a runoff process using seven independent parameters, evapotranspiration is simulated through another four parameters. The paper points out how the model can be successfully implemented in the simulation of diurnal discharge fluctuation on the small forested experimental catchment in dry periods.

Comparison of runoff characteristics of two adjacent basins in a tropical rainforest using a modified hydrologic cycle model with outflow

We propose a new runoff model including an outflow process that was applied to two adjacent basins (CL, TL) located in Lambir Hills National Park in north-central Sarawak, Malaysia. Rainfall, runoff, topography, and soil layer thickness were observed. About 19% of annual runoff was observed in the CL basin (21.97 ha), whereas about 46% was observed in the TL basin (23.25 ha). It was inferred that the CL basin has an outflow because of low base flow, small runoff peak, and excessive water loss. By incorporating the outflow process into the HYdrological CYcle MODEL, good agreement between the data generated by the model and that observed was shown, with the exception of the data from the rainless period. Then, the fitting parameters for each basin were exchanged, except for the outflow parameter, and the characteristics of each basin were compared by calculating virtual runoff. As a result, the low base flow of the CL basin was estimated by the movement of the rainwater that escaped from the basin as deep percolation or lateral flow (11% of rainfall). The potential of the CL basin for mitigating flood and drought appeared to be higher than that of the TL basin. This is consistent with the topographic characteristics of the CL basin, which has a gentler slope than the TL basin. Copyright © 2012 John Wiley & Sons, Ltd.