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Biocrust sustainability relies on dew and rain availability. A study of dew and rain resources in amplitude and frequency and their evolution is presented from year 2001 to 2020 in southern Africa (Namibia, Botswana, South Africa) where many biocrust sites have been identified. The evaluation of dew is made from a classical energy balance model using meteorological data collected in 18 stations, where are also collected rain data. One observes a strong correlation between the frequency of dew and rain and the corresponding amplitudes. There is a general tendency to see a decrease in dew yield and dew frequency with increasing distance from the oceans, located west, east and south, due to decreasing RH, with a relative minimum in the desert of Kalahari (Namibia). Rain amplitude and frequency decreases when going to west and north. Short-term dew/rain correlation shows that largest dew yields clearly occur during about three days after rainfall, particularly in the sites where humidity is less. The evolution in the period corresponds to a decrease of rain precipitations and frequency, chiefly after 2010, an effect which has been cyclic since now. The effect is more noticeable towards north. An increase of dew yield and frequency is observed, mainly in north and south-east. It results in an increase of the dew contribution with respect to rain, especially after 2010. As no drastic changes in the distribution of biomass of biocrusts have been reported in this period, it is likely that dew should compensate for the decrease in rain precipitation. Since the growth of biocrust is related to dew and rain amplitude and frequency, future evolution should be characterized by either the rain cycle or, due to global change, an acceleration of the present tendency, with more dew and less rainfalls.

Water is a significant primary resource on the Earth's surface. Fresh water is essential for human beings and for the stability and sustainable development of any nation. Many regions in the interior of Syria have an insufficient water balance. This has caused severe shortages of freshwater as a result of climate change. Syria's main source of fresh water, rivers and groundwater, suffers from low levels due to the lack of rainfall amounts. The war in Syria exacerbated water stress, in particular the effects of the war on water sources such as the Euphrates River and the ‘Feijah’ source that feeds the capital Damascus. All of this has prompted us to seek other non-traditional sources such as atmospheric water, which is a renewable and relatively clean source. This paper is considered to be the first of its kind in Syria. Experimental results from semi-arid and arid regions have shown good potential for harvesting dew and fog water as a supplementary and complementary source to the existing freshwater supply.

A plant's foliar uptake of dew can mitigate the adverse effects caused by drought stress. However, in grassland ecosystems, it is inconclusive whether the dew condensation characteristics of plants at different heights are consistent. In this study, we wanted to know whether plant height had a significant effect on the formation of dew. In addition, we wanted to understand the difference of dew formation between C3 plant Leymus chinensis (LC) and C4 plant Cleistogenes squarrosa (CS) which have different heights and can succeed each other in the community. In nine dew nights, we measured the amount of dew formed on simulated condensation surface (different heights) and two plants at the same time. The results showed that in the height range of 5–80 cm, the dew amount increases with the canopy height, but its increase rate gradually slows down and approaches zero. The shorter CS (5–15 cm) has a similar dew amount (0.095 mm) as LC (40–70 cm) due to its compact structure of the leaves with pubescence and the more stable micro-meteorological conditions. The CS can obtain more potential dew per unit organic matter, and this may be one of the potential mechanisms for the succession from LC communities to CS communities under drought stress. HIGHLIGHTS The dew formation on leaves theoretically changes exponentially with steppe plant height: y = a(1 − e−bx).; Both plant height and morphological characteristics affect dew formation.; One of the potential mechanisms of succession from Leymus chinensis (LC) community to Cleistogenes squarrosa (CS) community under drought stress was proposed.

Now a day the drinking water quantity is day by day going down due to some environmental conditions or climatic changes and water scarcity. The groundwater level also decreased in the summer season in comparing to other weather conditions. Generally, the water demand per day is 133per capita. In desert regions or low groundwater level areas the water consumption is very low and usage is also reduced. Minimizing water problems recycled water is used for plantation, garden works, construction work; etc.., So this reason the water saving is important and innovation is needed for the usage of water for any purpose, mainly needed to drinking. This project deals with the dew drain water analysis for drinking purposes. The characteristics of dew drain water match the natural water as per BIS.

Vapor condensation, whether due to dew or fog, may add a stable and important source of water to deserts. This was also extensively assessed in the Negev, regarded as a dew desert. Dew deserts necessitate a large reservoir of vapor, and are therefore confined to near oceans or seas. Yet, examples of such deserts are scarce. Here we try to assess whether the Tabernas Desert in SE Spain can be regarded as a dew desert, and may therefore facilitate the growth of certain organisms that otherwise would not survive the dry season. We analyze some of the abiotic conditions of four relatively dry months (June, July, August, September) in the Tabernas and Negev deserts (with the Negev taken as an example of a dew desert) during 2003–2012. The analysis showed substantially lower values of relative humidity (by 10–13%) in the Tabernas in comparison to the Negev, with RH ≥95% being on average only 0.9–1.1 days a month in the Tabernas in comparison to 9.7–13.9 days in the Negev. Our findings imply that the Tabernas Desert cannot be regarded as a dew desert, suggesting that rain will be the main factor responsible for the food web chain in the Tabernas.

Non-rainfall water (NRW), defined here as dew, hoar frost, fog, rime and water vapor adsorption, might be a relevant water source for ecosystems, especially during summer drought periods. These water inputs are often not considered in ecohydrological studies, because water amounts of NRW events are rather small and therefore difficult to measure. Here we present a novel micro-lysimeter (ML) system and its application which allows to quantify very small water inputs from NRW with an unprecedented high accuracy of ±0.25 g, which corresponds to ±0.005 mm water input. This is possible with an improved ML design paired with individual ML calibrations in combination with high-frequency measurements at 3.3 Hz and an efficient low-pass filtering to reduce noise level. With a set of ancillary sensors, the ML system furthermore allows differentiating between different types of NRW inputs: dew, hoar frost, fog, rime and the combinations among these, but also additional events when condensation on leaves is less probable, such as water vapor adsorption events. In addition, our ML system design allows to minimize deviations from natural conditions in terms of canopy and soil temperatures, plant growth and soil moisture. This is found to be a crucial aspect for obtaining realistic NRW measurements in short-statured grasslands. Our ML system has proven to be useful for high-accuracy, long-term measurements of NRW on short-statured vegetation like grasslands. Measurements with the ML system at a field site in Switzerland showed that NRW input occurred frequently with 127 events over 12 months, with a total NRW input of 15.9 mm. High average monthly NRW inputs were measured during summer months, suggesting a high ecohydrological relevance of NRW inputs for temperate grasslands., Hydrology and Earth System Sciences Discussions, ISSN:1812-2116, ISSN:1812-2108

Dew has been recognized as an important source of water for many coastal arid and semiarid ecosystems because of its contributions to daily, seasonal and annual water balance. We measured the frequency, duration and amount of dewfall from January 2011 to December 2016 to assess its contribution to the local water balance in a continental semiarid grassland where Bouteloua gracilis (Blue grama) is the key grass species. Dew was observed with leaf wetness sensors and amounts were estimated with an energy model using micrometeorological data. Dewfall occurred on 39% of the nights with an average duration of 5 ± 4 h. Daily average dewfall deposition during the study period was 0.2 mm with the highest accumulation of 0.7 mm. Annual dewfall ranged between 16.5 and 69 mm, therefore representing between 4.9% and 10.2% of annual precipitation. Dewfall contributed between 7.6% and 33.6% of the total dry season precipitation (winter/spring), which considerably reduced the water deficit. Our results highlight the relevance of dewfall as a consistent and important water source in this semiarid grassland ecosystem. It is of particular importance during dry periods, where it may represent the only water source available to the vegetation at this site.

© 2020 by the authors., Arid and semi-arid ecosystems are characterized by patchy vegetation and variable resource availability. The interplant spaces of these ecosystems are very often covered by cyanobacteria-dominated biocrusts, which are the primary colonizers of terrestrial ecosystems and key in facilitating the succession of other biocrust organisms and plants. Cyanobacterial biocrusts regulate the horizontal and vertical fluxes of water, carbon and nutrients into and from the soil and play crucial hydrological, geomorphological and ecological roles in these ecosystems. In this paper, we analyze the influence of cyanobacterial biocrusts on water balance components (infiltration-runoff, evaporation, soil moisture and non-rainfall water inputs (NRWIs)) in representative semiarid ecosystems in southeastern Spain. The influence of cyanobacterial biocrusts, in two stages of their development, on runoff-infiltration was studied by rainfall simulation and in field plots under natural rainfall at different spatial scales. Results showed that cover, exopolysaccharide content, roughness, organic carbon, total nitrogen, available water holding capacity, aggregate stability, and other properties increased with the development of the cyanobacterial biocrust. Due to the effects on these soil properties, runoff generation was lower in well-developed than in incipient-cyanobacterial biocrusts under both simulated and natural rainfall and on different spatial scales. Runoff yield decreased at coarser spatial scales due to re-infiltration along the hillslope, thus decreasing hydrological connectivity. Soil moisture monitoring at 0.03 m depth revealed higher moisture content and slower soil water loss in plots covered by cyanobacterial biocrusts compared to bare soils. Non-rainfall water inputs were also higher under well-developed cyanobacterial biocrusts than in bare soils. Disturbance of cyanobacterial biocrusts seriously affected the water balance by increasing runoff, decreasing soil moisture and accelerating soil water loss, at the same time that led to a very significant increase in sediment yield. The recovery of biocrust cover after disturbance can be relatively fast, but its growth rate is strongly conditioned by microclimate. The results of this paper show the important influence of cyanobacterial biocrust in modulating the different processes supporting the capacity of these ecosystems to provide key services such as water regulation or erosion control, and also the important impacts of their anthropic disturbance., This work has been supported by several research projects: REBIOARID (RTI2018-101921-B-I00), DINCOS (CGL2016-78075-P) projects, founded by the Spanish National Plan for Research and the European Union ERDF and the BIOCOST project Supported by Biodiversity Foundation of the Ministry for the Ecological Transition., Publisher’s version

Water moves continuously above and below the surface of the Earth. Bodies of water, clouds, evaporation and condensation all are part of the water cycle. Fog is composed of micron-sized water droplets that form when air becomes saturated with water vapor. Fog is a thick cloud that remains suspended in the atmosphere. Dew is the deposit of water droplets that are formed on cold surfaces, with temperature lower than the dew point, by condensation of water vapor in the air. In many plants and animals, living nature uses fog and condensation as a vital source of water, particularly in arid areas that receive little rainfall (Brown and Bhushan, 2016; Bhushan, 2018, 2019, 2020). Fog and dew always exist when the temperature decreases late at night and in the early morning. There is evidence that over 5000 years ago, hunter–gatherer groups were able to populate arid areas along the southern coast of Peru by utilizing fresh water from fog and condensation, though the collection method is unknown (Beresford-Jones et al. 2015).

The webs of hahniid spiders are poorly known. Those of Neoantistea riparia (Keyserling, 1887) all included sheets near the surface of the ground, but were more complex and variable than the simple sheets mentioned in previous accounts. Additional components included: sparse tangles of variable size above the sheet; lines below the sheet; small, dense tangles near some edges of the sheet; and a temporary feeding chamber below the sheet built near a recently captured prey. Webs were close to the surface of damp ground and, as a result, spent long periods coated with droplets of water. These droplets may aid in prey capture, as water accumulated on struggling prey and may have hindered their escape. In contrast, droplets seldom adhered to the spiders.

Fog and dew are often viewed as economic nuisances causing significant financial losses in the transportation industry and agricultural sector. However, they are also critical components of the hydrological cycle, especially in water scarce environments. Water scarcity is one of the major threats to mankind in the 21st century, and this can be due to development pressures, pollution, and/or expanding populations. In water scarce environments, fog and dew represent potentially exploitable ancillary water resources that could ameliorate the water scarce situation, if efficiently harvested. However, two important issues are often overlooked in relation to fog and dew harvesting and potability. First, current fog and dew harvesting technologies are low yielding with great potential for improvements. Second and more importantly, the potability of these water resources is often based on simple analyses that often omit trace metal and biological analyses. The few studies that report trace metal or biological measurements suggest elevated trace metal concentrations or biological contamination that could be of concern to public health. We discuss the potential for fog and dew harvesting technologies and the need for trace metal and biological analyses of these waters before use., Key Points Fog and dew are potential ancillary potable resources, but there are potential human health concernsCurrent fog and dew harvesting methods could be significantly improvedFog and dew should be treated before use as potable water

Dew harvesting can be a supplementary source of freshwater in semiarid and arid areas. Several experiments on small-scale dew condensers (usually of 1 m 2 ) have been carried out in many places in the world; however, few experiments have been conducted on large-scale collectors integrated into buildings. This work aims to assess one year of dew water harvesting in Combarbala (Chile) using a painted galvanised steel roof as collecting surface. The roof (36 m 2 ) was coated with a high-infrared-emissivity paint containing aluminosilicate minerals (OPUR, France). Dew measurements were conducted daily from September 2014 to August 2015. The dew yield and its relationship with meteorological variables were analysed. The results show that despite the low nocturnal relative humidity throughout the year (average: 48%), dew collection occurred on 56.1% of the recorded days. The daily average collection rate was 1.9 L d −1 , with a maximum of 15 L d −1 . The maximum daily dew yield is correlated strongly with relative humidity and correlated weakly with air temperature and wind speed. Considering the same rooftop can collect dew and rain, it was estimated that over one year dew water could contribute to roughly 8.2% of the total water collected, considering both sources.

Dewfall may be a critical source of moisture in desert environments and may determine sustainability of sand-stabilizing planted vegetation. However, little is known about factors responsible for dew formation, the relative importance of dew as a source of water, and its variability in plantations. During June and October of 2013, the dew amounts and duration were estimated by using the Bowen ratio energy budget technique (BREB), and the dew variability on sand dunes planted with Haloxylon ammodendron 5, 20, and 40 years before were measured by microlysimeter. We quantified dew formation characteristics in a sand-stabilizing H. ammodendron plantation at the edge of a desert oasis, northwestern China. The results indicated that the average daily amount of dew in the H. ammodendron plantations during the observation period based on BREB was 0.13 mm, and the dew duration lasted from 1 to 9.5 h. Dew occurred on 77% of growing season days, the number of days with dew amounts of >0.03 mm comprised 95% of the total dewfall days, and the cumulative amount of dew for those days was 16.1 mm. Air temperature, relative humidity, the difference between air temperature and dew point, and wind speed had significant effects on dew formation. The thresholds of the dew formation were RH >50% and wind speed

The seasonally-dry climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. Frequently during summer, the only water inputs occur as non-rainfall water, in the form of fog and dew. However, due to spatially heterogeneous fog interaction within a watershed, estimating fog water fluxes to understand watershed-scale hydrologic effects remains challenging. In this study, we characterized the role of coastal fog, a dominant feature of Northern Californian coastal ecosystems, in a San Francisco Peninsula watershed. To monitor fog occurrence, intensity, and spatial extent, we focused on the mechanisms through which fog can affect the water balance: throughfall following canopy interception of fog, soil moisture, streamflow, and meteorological variables. A stratified sampling design was used to capture the watershed's spatial heterogeneities in relation to fog events. We developed a novel spatial averaging scheme to upscale local observations of throughfall inputs and evapotranspiration suppression and make watershed-scale estimates of fog water fluxes. Inputs from fog water throughfall (10–30 mm/year) and fog suppression of evapotranspiration (125 mm/year) reduced dry season water deficits by 25% at watershed scales. Evapotranspiration suppression was much more important for this reduction in water deficit than were direct inputs of fog water. The new upscaling scheme was analyzed to explore the sensitivity of its results to the methodology (data type and interpolation method) employed. This evaluation suggests that our combination of sensors and remote sensing allows an improved incorporation of spatially-averaged fog fluxes into the water balance than traditional interpolation approaches.

Dew is an important water source for plants in arid and semi-arid regions. However, information on dew is scarce in such regions. In this study, we explored dew formation, amount, and duration of rain-fed jujube (Zizyphus jujube Mill) trees in a semi-arid loess hilly region of China (i.e., Mizhi County). The data included dew intensity and duration, relative humidity, temperature, and wind speed measured from 26 July to 23 October, 2012 and from 24 June to 17 October, 2013 using a micro-climate system (including dielectric leaf wetness sensors, VP-3 Relative Humidity/Temperature Sensor, High Resolution Rain Gauge, and Davis Cup Anemometer). The results show that atmospheric conditions of relative humidity of >78% and dew point temperature of 1°C–3°C are significantly favorable to dew formation. Compared with the rainfall, dew was characterized by high frequency, strong stability, and long duration. Furthermore, heavy dew accounted for a large proportion of the total amount. The empirical models (i.e., relative humidity model (RH model) and dew point depression model (DPD model)) for daily dew duration estimation performed well at 15-min intervals, with low errors ranging between 1.29 and 1.60 h, respectively. But it should be noted that the models should be calibrated firstly by determining the optimal thresholds of relatively humidity for RH model and dew point depression for DPD model. For rain-fed jujube trees in the semi-arid loess hilly regions of China, the optimal threshold of relative humidity was 78%, and the optimal upper and lower thresholds of dew point depression were 1°C and 5°C, respectively. The study further demonstrates that dew is an important water resource that cannot be ignored for rain-fed jujube trees and may affect water balance at regional scales.

The use of micro-lysimeters (MLs) by the scientific community for the measurement of non-rainfall water input, NRWI (dew, fog, water vapor) has become more widespread. With MLs being isolated bodies, we hypothesized that changes in heat flux may affect the surface temperatures and subsequently NRWI. Measurements were conducted with MLs of various lengths (3.5, 12, 20, 30, 40, 50 cm for 2014 and 3.5, 12, 50 cm for 2015), and on the adjacent soil that served as a control (COT) using cloths attached to glass plates in Sede Boqer (Negev Desert, Israel) during the late summer and fall of 2014 and 2015. In addition, periodical temperature and moisture measurements were also conducted on additional lysimeters. Non-significant differences in NRWI characterized MLs 12–50 cm-long, which could have been therefore grouped (termed ML12/50). However, these lysimeters and especially the 3.5 cm-long ML (ML3.5) yielded substantially higher values than that of COT, with the ratio of ML12/50 to COT and the ratio of ML3.5 to COT being up to 2.4 and 5.8, respectively, implying, as was indeed found during periodic measurements, lower nocturnal temperatures and subsequently higher moisture content at 0–0.2 cm at the MLs in comparison to COT. This was also reflected in the amount of recorded mornings with effective (>0.03 mm) NRWI: 34 mornings based on the ML12/50 in comparison to only 4 when based on COT. The findings raise serious concerns regarding published data on NRWI and call for proper calibration between the amounts obtained by the MLs and the natural intact soil.

Precipitation is usually the primary source of water for the hydrological cycle in a semi-arid area. However, dew occurs frequently and affects water circulation dramatically in the west of Jilin Province in China. Measurements of the amount of dew formed and precipitation were carried out from July 2012 to October 2013 in the Momoge Natural Reserve. The results indicated that moisture from primary precipitation in the summer originated from the East Asian Monsoon and was affected by the atmospheric circulation in the middle and high latitudes of Eurasia in the winter. The dew amount was approximately 19.44 mm (approximately 5% of the total rainfall amount), consisting of the evapotranspiration in the local area and atmospheric moisture. Dew also supplies nutrients to the local vegetation. The maximum contribution of total nitrogen (TN), total phosphorus (TP) and potassium (K) in unit corn area could reach 288.60 mg/m2, 27.46 mg/m2 and 291.63 mg/m2 in half a month, respectively. The wind speed, relative humidity and lowest temperature were the primary factors that dramatically affected dew formation and amount. As an additional source of fresh water, dew not only had a positive impact on the ecosystem in arid and semi-arid zones but also played an important role in the local water cycle and other ecological processes. This research has important implications for water circulation and land use management.

The quality and chemical composition of urban dew collections with dust precipitates without pre-cleaning of the collecting surface WSF (white standard foil) were investigated for 16 out of 20 collected samples with collected volumes ranging from 22 to 230 ml. The collection period was from March to July 2015 at an urban area, Jubaiha, which is located in the northern part of the capital city Amman, Jordan. The obtained results indicated the predominance of Ca2+ and SO42− ions (ratio 2.2:1) that originated from Saharan soil dust; where the collected samples were alkaline (mean pH = 7.35) with high mineralization (429.22 mg/L) exceeding the previously reported dew values in Amman-Jordan. A relocation of NaCl and to a less extent Mg2+ from sea to land by Saharan wind is indicated by the percent sea-salt fraction calculations (over 100 and 52, respectively). The collected samples exhibited high total organic carbon (TOC) values ranging from 11.86 to 74.60 mg/L, presence of particulate settled material with turbidity ranging from 20.10 to 520.00 NTU, and presence of undesired elements like boron (mean = 1.48 mg/L) that made it different in properties from other dew water collections at clean surfaces, and exceeding the standard limits for drinking water for these parameters set by Jordanian Drinking Water standards (JS286/2015)/WHO standard. The quality of this water is more close to that for raw or agricultural water but if it is meant to be used as potable source of water, at least sand and activated charcoal filters are needed to purify it.

Leaf wetness (LW) is a key environmental variable for the development of foliar fungal diseases of citrus. However, little information of LW duration (LWD) in Mediterranean citrus-growing areas is available. LWD in six canopy positions and two leaf sides was studied with visual observations and Spectrum LW sensors in a citrus orchard in Spain. The performance of Spectrum and Hobo LW sensors, and CART/SLD and RH LW models was assessed by receiver operating characteristic (ROC) curve analysis. The dynamics of LWD in three citrus orchards with flood irrigation and three with drip irrigation were evaluated using time-series models. LWD data from all experiments and recordings in 14 commercial citrus orchards illustrated the high frequency of LW periods, particularly those associated with dew. No substantial differences in LWD were detected among citrus canopy positions and leaf sides. An optimal dry/wet threshold of 2.85 for the Spectrum LW sensor, 75.88 for the Hobo LW sensor, 15.99 for the CART/SLD model, and 87.45% for the RH model was selected by ROC curve analysis. All the sensors and models evaluated showed a substantial strength of agreement with visual observations of LW, with area under the ROC curve of 0.89–0.93 and Cohen’s Kappa index of 0.61–0.77. The RH model was recommended because of easier implementation in citrus orchards in Spain. Time-series models did not detect any significant increase in LWD associated with flood irrigation, but only after some rain events. High mesoclimatic relative humidity in the study area outweighed possible microclimatic changes induced by flood irrigation. Thus, negligible effects of flood irrigation in the infection of foliar fungal pathogens would be expected, but longer LWD in the lower canopy as well as potential effects on inoculum dynamics in the leaf litter cannot be excluded.

Non-conventional water resources have emerged as means to meet or supplement irrigation demand for reforestation and agriculture in water scarce regions. Dew water is among those resources that have received little attention. In this paper, we compare reforestation and agriculture water demands to measured dew volumes to assess the feasibility of irrigation from dew harvesting. We estimate water demands of selected crops and trees seedlings using evapotranspiration (ET)-based modelling, while corresponding dew volumes were experimentally measured during the dry season. Field data collected from dew condensers (1 m 2 ) showed that 43% of nights produced dew during the dry season (April–October) with average nightly dew yield of 0.13 L m −2 of condensing surface and a maximum yield of 0.46 L m −2 d −1 . Experimental results showed that dew events are more frequent than precipitation events and harvested dew can significantly impact diurnal soil moisture (>3%) during evenings with above average nightly dew yields (>0.2 L m −2 d −1 ). We demonstrate that harvesting and storing dew using reasonable condensing areas (∼2 m 2 ) can be sufficient to irrigate tree seedlings, typically requiring ∼4.5 L/seedling every 30-40 days, thus providing a feasible option mitigating tree mortality during droughts or in arid or semi-arid regions. Moreover, these low-cost stand-alone systems can prevail in remote locations where infrastructure and traditional water resources are limited.

Dew can serve as an important source of moisture for plants, biological crusts, insects and small animals in arid and semiarid basin. Dew amount and the relationship between sand dew and plant leaf dew were analyzed to understand dew transformation law under different condensation surfaces and its significance in irrigation water supplementation. During April 1–May 31, and September 1–October 31, 2018, field monitoring was carried out at the groundwater and environment site of Chang’an University, in Guanzhong Basin, China, using weighing method for sand dew measure, as well as leaf wetness sensors for plant leaf dew measure. Results showed that both sand dew and leaf dew manifested “high frequency and low amount” pattern. Their dew days (69 days, 66 days) accounted for 80% and 77% of rainless days (86 days), but dew amount (6.56 mm, 14.75 mm) accounted for 3.3% and 7.4% of rainfall (198.2 mm) in the same period, respectively. The average daily dew amount for sand was 0.054 mm with a daily maximum of 0.22 mm, and that for plant leaf was 0.12 mm with a daily maximum of 0.78 mm. Average daily leaf dew amount was about 2.2 times that of sand dew amount. Sand dew amount (W) was highly and positively correlated to leaf dew amount (D), and the fitting equation was W = 0.237 × D + 0.044 (p

To determine the effect of sensor placement on the performance of a disease-warning system for sooty blotch and flyspeck (SBFS), we measured leaf wetness duration (LWD) at 12 canopy positions in apple trees, then simulated operation of the disease-warning system using LWD measurements from different parts of the canopy. LWD sensors were placed in four trees within one Iowa orchard during two growing seasons, and in one tree in each of four orchards during a single growing season. The LWD measurements revealed substantial heterogeneity among sensor locations. In all data sets, the upper, eastern portion of the canopy had the longest mean daily LWD, and was the first site to form dew and the last to dry. The lower, western portion of the canopy averaged about 3 h less LWD per day than the top of the canopy, and was the last zone where dew formed and the first to dry off. On about 25% of nights when dew occurred in the top of the canopy, no dew formed in the lower, western canopy. Intracanopy variability of LWD was more pronounced when dew was the sole source of wetness than on days when rainfall occurred. Daily LWD in the upper, eastern portion of the canopy was slightly less than reference measurements made at a 0.7-m height over turfgrass located near the orchard. When LWD measurements from several canopy positions were input to the SBFS warning system, timing of occurrence of a fungicide-spray threshold varied by as much as 30 days among canopy positions. Under Iowa conditions, placement of an LWD sensor at an unobstructed site over turfgrass was a fairly accurate surrogate for the wettest part of the canopy. Therefore, such an extra-canopy LWD sensor might be substituted for a within-canopy sensor to enhance operational reliability of the SBFS warning system.

Water scarcity is increasingly raising the need for non-conventional water resources, particularly in arid and semi-arid regions. In this context, atmospheric moisture can potentially be harvested in the form of dew, which is commonly disregarded from the water budget, although its impact may be significant when compared to rainfall during the dry season. In this study, a dew atlas for the Mediterranean region is presented illustrating dew yields using the yield data collected for the 2013 dry season. The results indicate that cumulative monthly dew yield in the region can exceed 2.8mm at the end of the dry season and 1.5mm during the driest months, compared to

Spatial variability in lithobiont-induced weathering patterns on desert rocks is aspect-dependent. While differences between the northern and southern aspects have been extensively studied, little is known concerning the differences between east-facing (EF) and west-facing (WF) aspects in deserts, including the Negev Desert. Whereas cobbles on both slopes are inhabited by endolithic lichens, epilithic lichens, which render the bedrock a smooth appearance, and free-living cyanobacteria, which give the bedrock a rugged microrelief, predominate on WF and EF bedrock, respectively. Following previous research that regarded dew as the principal factor that determines lithobiont distribution, measurements of radiation, temperature, wind and dew were carried out during 2008–2009 in the Negev Desert. The data indicated that albeit slightly higher midday surface temperatures that characterize WF surfaces (cobbles and bedrock), nocturnal temperatures on these surfaces were significantly lower, therefore facilitating higher dew condensation. High amounts of dew result from the relatively rapid drop in temperatures (14:00–20:00) due to the afternoon northwesterly sea-breeze wind (with a cooling rate of the WF bedrock being 52.9% higher than on EF bedrock, 2.6 °C h−1 in comparison to only 1.7 °C h−1), and facilitate the growth of high-chlorophyll dew-fed (and rain-fed) epilithic lichens, which may act as bio-protectors on WF bedrock. Lack of condensation on EF bedrock results in turn in the growth of rain-fed free-living cyanobacteria, responsible for high rock dissolution and subsequently for a rugged microrelief. By affecting the nocturnal bedrock temperatures, wind acts as a cooling agent, impacting in turn the amount of dew, and subsequently lithobiont composition and weathering patterns in the Negev Desert. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

25 Pags.- 6 Figs.- 2 Tabls. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Accumulated daily crop evapotranspiration (ETc) generally provides good estimates of cumulative soil water depletion between irrigation of well drained soils. If the canopy is wet due to fog, dew, or light rainfall, however, energy contribution to surface evaporation will reduce transpiration and hence soil water losses. When surface evaporation occurs, the ETc overestimates the soil water depletion by an amount approximately equal to the surface water evaporation. Moratiel et al. (2013) proposed a method to estimate the contribution of surface water to ETc based on the time of canopy drying. The first method assessment was done with California data, and this evaluation was conducted in the Ebro basin, Spain, to appraise the method in a higher latitude in area with a somewhat different climate. Differences between the California and Spain corrected models were less than 10% and depended mainly on the time of canopy drying. The comparison showed that the model is robust and useful to estimate the fraction (F) of ETc coming from the soil under dew, light rainfall, and fog conditions., Thanks are due to Ministry of Agriculture, Food and Environment for facilitating data collection.

We present year round meteorological and conductivity measurements of colonized hypolithic rocks in the Arava Valley, Negev Desert, Israel. The data indicate that while dew is common in the Negev it is not an important source of moisture for hypolithic organisms at this site. The dominance of cyanobacteria in the hypolithic community is consistent with predictions that cyanobacteria are confined to habitats supplied by rain. To monitor the presence of liquid water under the small Negev rocks we developed and tested a simple field conductivity system based on two wires placed about 0.5 cm apart. Based on 21 replicates recorded for one year in the Negev we conclude that in natural rains (0.25 mm to 6 mm) the variability between sensor readings is between 20 and 60% decreasing with increasing rain amount. We conclude that the simple small electrical conductivity system described here can be used effectively to monitor liquid water levels in lithic habitats. However, the natural variability of these sensors indicates that several replicates should be deployed. The results and method presented have use in arid desert reclamation programs.

In arid and semiarid environments, where precipitation is scarce and mainly limited to the wet season of the year, the water contribution by non-rainfall water inputs (NRWI) may play a significant role in the water balance. Natural ecosystems are heterogeneous with a great variety of surface covers, such as stones, biological soil crusts (BSC), bare soil, trees, shrubs and other plants. To be able to understand the role that NRWI may have in a system, all the surface types involved and all the NRWI sources (fog, dew and water vapour adsorption) should be differentiated, analyzed and studied separately. This manuscript study NRWI on different cover surfaces of the soil in a natural coastal-steppe ecosystem. Automated microlysimeters were located in the field containing small Macrochloa tenacissima plants, bare soil, stones and biological soil crusts. Daily changes in the water content of the samples were registered. The different sources of NRWI were differentiated and their partial contributions to the total NRWI and to the daily evaporation were analyzed. Each cover type showed a different response in the presence of NRWI and these responses were also dependent on the NRWI source. In turn, the surface cover influenced the subsequent evaporation the day after. The number of dew events varied with the surface cover type and water vapour adsorption occurred all days in all the covers, alone or preceding a fog or a dew event. Dew represented the main NRWI source in plants and stones, while water vapour adsorption was the main input in bare soil and BSC. Fog was a minor component of the NRWI during the study period and its partial contribution to the total input was similar for all the cover types. NRWI satisfied a great part of the evaporation in the sample, especially in plants and stones.

Dew is an important source of water which significantly influences the physiological status of vegetation and the microclimate environment. For quantifying the characteristics of dew events and analyzing the underlying mechanism of dew formation in different ecosystems, we measured, based on the flux-profile method, the amount, frequency and duration of dew events in two croplands, an arid artificial oasis cropland in Zhangye, Gansu province and a sub-humid cropland in Luancheng, Hebei province in China. The results showed that dew events were observed in a total of 69 days in Zhangye, which accounted for 59% of the growing season (from 28 May to 21 September, 2012), while 128 days in Luancheng, which accounted for 79% of the growing season (from 5 April to 13 September, 2008). The frequencies of dew events were 2.8 and 2.4 times of those of precipitation in Zhangye and Luancheng, respectively. In addition, the dew amount reached up to 9.9 and 20.2 mm in Zhangye and Luancheng, which accounted for 9.5% and 4.1% of precipitation, respectively. The average amount of dew was 0.14 and 0.16 mm/night in Zhangye and Luancheng, respectively and the duration of dew events ranged from 0.5 to 12.0 h in the two study sites. Dew amounts were associated with the gradient of atmospheric water vapor concentration and dew duration (P

The measurements of dew formation efficiency and chemistry were performed in Poland in September 2009, as a part of a longer, two-year sampling campaign. Pairs of sites, representing centers of major Polish cities and rural conditions in three different regions, were compared. With the aim to get more detailed landuse-oriented characteristics of dew, two additional sites were set close to Wroclaw. Collection of dew at each site was made by means of flat, insulated, passive radiative condenser, 1 m 2 in area. The analysis has included a number of physico-chemical variables, i.e.: dew water volume, pH, conductivity (σ), concentration of some major anions: F − , Cl − , NO 2 − , NO 3 − , SO 4 2 − , PO 4 3 − and cations: Na + , K + , Mg 2+ , Ca 2+ , NH 4 + . The dew formation efficiency at the rural stations is about two times higher than in the nearby city centres and such regularity is complex in its origin. The results show generally low contamination of dew (16.8–132.6 μS cm −1 ) in comparison to literature examples, but definitely more acidic (pH ∼5.0). The urban dew is characterized about two times higher contamination than nearby rural and independently of the place of collection the dominant ions are NO 3 − , SO 4 2 − and Ca 2+ , all anthropogenic in origin. The sources of dew pollution have mostly regional character or alternatively urban emissions effectively contaminate dew even several tens of kilometers away. The urban dew pH is higher than rural, but dew is potentially acidic and corrosive at the level of urban canopy.

Waste rock dumps in the aftermath of pegmatite mining enable the growth of healthy populations of Larix sibirica in, for the forest unsuitable semi-arid steppe habitat, the Khentii Mountains, Mongolia. Trees can thrive in such extreme habitats due to water vapour condensation and adsorption in the topsoil of a dump. During the growing season 2015–2017, continual measurement of thermal regime (hourly) was carried out at the depths of 10, 30 and 60 cm in the dumps and surrounding steppes. At the depth of 10 cm, temperatures (up to 40% of cases) enabling dew formation in dumps, in the time period of the highest possible air humidity (2 a.m. to 8 a.m.) were confirmed there. The suitable temperature conditions to form dew were found primarily at the beginning of the growing season characterized by a low precipitation. Later in the growing season with the following increasing precipitation, the temperature potential of dumps for dew formation decreased continuously. The cross-correlation indicated active exchange of heat between the atmosphere and the dump up to the depth of 30 cm. The outcomes further indicate that water vapour adsorption shall contribute significantly to the moisture regime of dumps and the effective porosity of sandy soils of dumps is likely to form ideal conditions for it. The construction thickness of the cover soil material between the depths of 30 and 60 cm with the predefined physico-chemical properties can be recommended to augment the potential of the dew yield in future projects. Effective water vapour condensation and adsorption may support success of landscape afforestation or reclamation of mining areas in arid or semi-arid conditions.

Atmospheric water absorption by plants has been explored for more than two centuries, and the aerial parts of plants, particularly the leaves of certain species, have been demonstrated to have an ability to absorb and utilize saturated atmospheric water such as fog, dew and condensed water. So far, however, there have been few studies on the aerial parts of desert plants in their absorption of unsaturated water from the atmosphere. This study presents an ultrasonic humidification fluorescent tracing method of detecting unsaturated atmospheric water absorption by the aerial parts of desert plants. We constructed an organic glass room based on the sizes of field plants. Then, the aboveground parts of the plants were humidified in the sealed glasshouse using an ultrasonic humidifier containing fluorescent reagents. The humidity and wetting time were controlled by turning on or off the humidifier according to the reading of a thermo-hygrometer suspended in the glasshouse. Fluorescence microscopy was employed to observe these plant samples. This method can generate unsaturated atmospheric water vapor and incorporate other fluorescent reagents or water-soluble chemical reagents for gasified humidification. In addition, it can identify plant parts that absorb unsaturated atmospheric water from the air, detect water absorption sites on the surface of leaves or tender stems, and determine the ability of tissues or microstructure of aerial parts to absorb water. This method provides a direct visual evidence for the inspection of leaf or tender stem microstructure in response to unsaturated atmospheric water absorption. Moreover, this method shows that aqueous pores in the cuticles of leaves or tender stems of desert plants are large enough to allow the passage of ionic fluorescent brightener with a molecular weight of up to 917 g/mol. Thus, this paper provides an important approach that explores the mechanism by which desert plants utilize unsaturated atmospheric water.

Dew deposition is an ecologically important phenomenon in many coastal drylands, but its measurement remains difficult. We report the construction and field-testing of a sturdy device to digitally determine dew deposition during night and early morning hours. Balance readings were compared with dew deposition measurements taken by alternative methods: a plastic sheet of 2 m × 3 m laid out on sandy ground, a plastic sheet of 1 m × 2 m laid out at 1 m height on a wooden surface, and a plastic sheet laid out at 1 m height on a metallic surface. Daily dew deposition rates on our device ranged from 0.055 to 0.192 mm between months with maxima reaching 0.479 mm. Dewfall amounted to 58.4 mm and represented 19% of annual rainfall after the whole observation period of 18 months. Correlation coefficients between the different measuring methods amounted to r = 0.71 (balance – plastic sheet on the ground), r = 0.84 (balance – 1 m high plastic sheet on wooden surface), r = 0.82 (balance – 1 m high plastic sheet on metal surface) and r = 0.99 (1 m high plastic sheet on wooden surface – 1 m high plastic sheet on metal surface). Our results suggest that in coastal south-western Madagascar dewfall plays a role in the annual water balance, but its ecological significance remains to be investigated.

Repeated loss of fine soil particles by dust emission from arable fields caused by tillage operations, decline soil fertility and reduce air quality. The objective of this study was to quantify the diurnal dynamic of topsoil moisture and the connected PM 10 -emission of 15 different soils from arable fields around Berlin. As typical for the young moraine landscape in NE Germany, soils from glacial (sand and loam dominated), aeolian (silt loam), and fluvial (organic) sediments were selected. Soil samples were placed outside under hot summer and clear sky conditions for 24 h to reproduce the natural dynamic of soil surface moisture, including dew uptake during the night and evaporation during the day. Dynamic of PM 10 emissions of all soils were then measured nine times per day in a stationary wind tunnel. Glacial and fluvial sands showed lowest fine dust emission potential (PM 10pot ) between 89 and 415 μg PM 10 g −1 soil, while PM 10pot of loess soils were higher (369–1215 μg PM 10 g −1 soil). During the night, the moisture of all samples increased slightly by dew uptake, and fine dust emissions of soil samples were reduced up to 51% directly after sunrise. Highest average reductions in PM 10 emissions were found for glacial and fluvial loams. Some hours after sunrise, all soil samples heated up and quickly dried again. Under minimal moisture conditions, highest fine dust emissions were measured between 10 a.m. and 3 p.m.

In this study, five passive radiative surfaces were analyzed for dew formation in south-eastern Spain; a dew condenser (RDC), a modified Class-A pan evaporimeter, the water stored in an open pond, the water stored in a covered pond, and the suspended shade cloth cover which covered the pond. In the case of the RDC and the pan, two different modeling approaches were used to estimate dew: (i) dew was correlated with meteorological variables and (ii) dew was derived from the mass transfer equation. In the other three cases, dew formation was assessed by analyzing the difference between the dew point and the water surface temperature. The RDC was more productive than the pan as the latter cooled less overnight and also underwent interspersed processes of evaporation and condensation. In the case of the RDC, both modeling approaches gave satisfactorily estimates whilst they were less accurate for the pan. On the water bodies, the water thermal inertia usually maintained the night water surface temperature above the dew point and strongly limited the dew formation. On the contrary, dew has been proven to exist on the cover, although the low amounts of dew deposited hinder its drainage to the water.

Summary The extent to which the finite hydrological capacity of a green roof is available for retention of a storm event largely determines the scale of its contribution as a Sustainable Drainage System (SuDS). Evapotranspiration (ET) regenerates the retention capacity at a rate that is variably influenced by climate, vegetation treatment, soil and residual moisture content. Experimental studies have been undertaken to monitor the drying cycle behaviour of 9 different extensive green roof configurations with 80 mm substrate depth. A climate-controlled chamber at the University of Sheffield replicated typical UK spring and summer diurnal cycles. The mass of each microcosm, initially at field capacity, was continuously recorded, with changes inferred to be moisture loss/gain (or ET/dew). The ranges of cumulative ET following a 28 day dry weather period (ADWP) were 0.6–1.0 mm/day in spring and 0.7–1.25 mm/day in summer. These ranges reflect the influence of configuration on ET. Cumulative ET was highest from substrates with the greatest storage capacity. Significant differences in ET existed between vegetated and non-vegetated configurations. Initially, seasonal mean ET was affected by climate. Losses were 2.0 mm/day in spring and 3.4 mm/day in summer. However, moisture availability constrained ET, which fell to 1.4 mm/day then 1.0 mm/day (with an ADWP of 7 and 14 days) in spring; compared to 1.0 mm/day and 0.5 mm/day in summer. A modelling approach, which factors Potential Evapotranspiration (PET) according to stored moisture content, predicts daily ET with very good accuracy (PBIAS = 2.0% [spring]; −0.8% [summer]).

Different peatland mosses have varying strategies for water storage and capillary rise mechanisms depending on their particular hydrophysical properties and preferred water sources. To understand these strategies, the retention and redistribution of water from various sources in Sphagnum, feather and Tomenthypnum moss communities were addressed through investigation of the sensitivity of moss moisture dynamics to environmental variables, field surveys and a drought stress experiment. Feather mosses preferred habitats well above the water table, and their relatively low volumetric water content (θ) increased only with precipitation events. The relatively high residual θ (0·22) of Sphagnum capitula helped the moss type maintain conditions suitable for photosynthesis over a range of water table conditions. Tomenthypnum mosses occurred over a broader range of water table positions than Sphagnum or feather mosses because of their ability to use both capillary rise and atmospheric water for growth. While Tomenthypnum had relatively low near-surface θ (~0·10), evaporative losses were sustained by both small nocturnal additions by condensation of vapour and upward capillary rise. An intermediate layer of partially decomposed mosses supported contact with the underlying peat and helped transport sufficient water to the Tomenthypnum moss surface. However, Tomenthypnum θ and productivity changes were more sensitive to rainfall additions as the uppermost portion of moss shoots can easily desiccate under typical evaporative demand. As a result, nocturnal sources of atmospheric water from dew (~0·15mm per night) and distillation (~0·10mm per night) provided temporary relief from desiccation for potentially important early morning photosynthesis and helped drive evaporation and capillary rise. Copyright © 2015 John Wiley & Sons, Ltd.

Differences in vegetation pattern between slope aspects in semiarid environments are well known, with shaded aspects presenting a higher biomass. The micrometeorological and soil conditions involved in non-rainfall water inputs (NRWI), comprising dew and water vapour adsorption (WVA) were compared between two contrasted slopes and different environmental conditions (wet and dry periods). Changes in natural soil surfaces were measured using automated microlysimeters, and the partial contributions of dew and WVA to the total NRWI were clarified. Dew amounts were higher on the northeast facing slope and were directly related to dew durations. Differences in dew deposition between slopes were mainly driven by insolation patterns, which controlled the surface temperatures, the soil water content and, in turn, dew duration. Apart from spatial variation in microclimate, WVA deposition was higher in the southwest facing slope due to its higher clay content and electric conductivity and because of its lower soil water content. Water vapour adsorption was directly governed by the relative humidity amplitude in summer (with dry soil) but not in winter. A significant amount of water evaporation was satisfied by NRWI, reaching 100% in dry periods and being WVA the main input.

The global potential for collecting usable water from dew on an artificial collector sheet was investigated by utilizing 34 years of meteorological reanalysis data as input to a dew formation model. Continental dew formation was found to be frequent and common, but daily yields were mostly below 0.1 mm. Nevertheless, some water-stressed areas such as parts of the coastal regions of northern Africa and the Arabian Peninsula show potential for large-scale dew harvesting, as the yearly yield may reach up to 100 L m−2 for a commonly used polyethylene foil. Statistically significant trends were found in the data, indicating overall changes in dew yields of between ±10% over the investigated time period.

Due to global warming, a drying and warming trend has been observed over the last 50 years in the Sanjiang Plain of Heilongjiang Province, China, which could significantly affect the condensation of vapor in paddy ecosystems. Dew is a crucial factor in the water and nutrient cycling of farmland ecosystems, and it exerts an important influence on fertilization and other agricultural activities. In order to reveal the effects of global warming on dew variation in a paddy ecosystem, anin situexperiment was conducted in paddy fields in the Sanjiang Plain during the growing seasons of 2011 to 2013. Dew was collected and measured with a poplar stick. The results of correlation analysis between meteorological factors and dew intensity in the paddy ecosystem indicate that the dew point temperature and relative humidity significantly influenced the dew intensity. Based on synchronous meteorological data, a stepwise linear multivariation regression model was established to predict dew amount. The model successfully interpreted the relationship between simulated and measured dew intensity. The results suggest that a warmer and drier climate would lead to a reduction in dew amount because water cannot condense when relative humidity falls below 71%.

Rain in the summer monsoon season is the main water input for the water cycle in the alpine meadow ecosystem of Northern Tibet, however, dew has been observed frequently in Nagqu, especially during consecutive dry days. Under climate change and human disturbance, degradation of the meadow leads to surface property changes and these may affect dew formation. The amount of dew formed on top of the vegetation surface was therefore measured on normal Kobresia pygmaea meadow and partly-degraded crusted meadow soil for 12 dew days in the 40 observation days from early-July to mid-August in 2011. The converted average daily dew depth was significantly higher on the normal meadow and the average of 0.15 mm/night was three times that on the degraded surface between 20:00 and 7:00. To qualitatively identify the role of dew in the local water cycle, water samples from atmospheric water vapour, rain, creek water and groundwater were collected in July and August of 2011 for the analysis of stable water isotopes using the isotope ratio infrared spectroscopy method (IRIS); the vapour samples were collected by cryogenic trapping. It is shown in a δD–δ18O space that the dew contains water that has been terrestrially recycled by evapotranspiration. This research takes an initial step to see the impact of meadow degradation on dew formation, with regard to its formative conditions and moisture source, suggesting that dew may be an active water source for meadow growth and hydrological processes during summer dry spells on the high plateau.

This article presents the results of a research study concerning a comparison of frequency, formation efficiency and basic physico-chemical properties of dew and hoarfrost in urban conditions. Longer than two-year series of measurements was carried out from 1 February 2008 to 10 March 2010 in Wroclaw, Poland. Sampling of atmospheric deposits was made by means of insulated plain passive radiative condensers, which allowed to collect 222 dew and 96 hoarfrost samples. The results indicate that the frequency of dew days was about threefold greater than hoarfrost days. The formation efficiency of both types of deposits was almost the same, and reached a mean value of about 100 mL·m − 2 per day. The conducted analysis of several meteorological parameters showed that dew and hoarfrost, despite seasonal weather changes, were formed in very similar meteorological conditions. Only water vapor pressure values were in average twice higher in the case of dew and the impact of this parameter on dew and hoarfrost formation efficiency seems to be more complex than expected. The role of night duration in counterbalancing of smaller amount of available moisture in hoarfrost days is not clear. The investigation showed also, that there was an expected clear positive dependence of dew and hoarfrost formation efficiency on relative humidity, and not so evident in the case of temperature inversion, and wind velocity. The physico-chemical analysis indicated that the pH of dew was only slightly lower than the hoarfrost ones, regardless of the deposit formation intensity. Simultaneously, the lower pH values were much more frequent in the case of dew, which resulted from more effective absorption of anthropogenic NO 3 − and SO 4 2 − ions. For both types of deposits, the average pH was low (4.5–4.8) in relation to majority of studies reported in literature. In spite of seasonal changes of pollutant concentration, various weather conditions and different mechanisms of pollutant absorption of dew and hoarfrost were characterized with almost identical, relatively low contamination — electric conductivity: 42 μS·cm − 1 . The dominant ions were: Ca 2 + , SO 4 2 − , NO 3 − , as well as Cl − (hoarfrost only), all of them predominantly of anthropogenic origin.

Dew and rain water were collected during 2013 and 2014 in Changchun, China. The dew was analyzed and the following parameters were measured: pH, EC, TDS, major anions (F−, Cl−,SO42-, andNO3-), and major cations (NH4+, Na+, K+, Ca2+, and Mg2+). The mean pH, EC, and TDS values of dew were comparable with the values for rainwater. The pH values of dew and rain were 6.72 and 6.16, respectively. Both EC (308 μS/cm) and TDS (154 mg/L) of dew were higher than those in rain samples. The concentration of main ions in dew was 1.5–5.7 times higher than levels in rainwater. The near-neutral pH values in dew were caused by the neutralization of acidity and buffering by the alkaline elements of soil origin (Ca2+). This neutralization was confirmed by a strong correlation between the acidic ions (SO42-andNO3-) and the major cations (Ca2+and Mg2+). Natural dust made an important contribution to the ions present in dews, but the presence of sulfate concentrations that are notably higher than rain water (up to 1584.5 μeq/L) indicated a significant contribution of anthropogenic sources. Dew has the ability to capture particulates, and the purifying effect on the underlying surface was obvious.

Although precise weighing lysimeters are mostly installed for agricultural purposes in crop-producing areas, these instruments are also useful in areas of ecological interest where soil and aquifer recharge-discharge processes need to be better understood. In September 2015 a high precision meteo-lysimeter was installed in a coastal dune of the Donana Natural Reserve to quantify the recharge in dune belts, and to estimate its dependence on regional climate trends. In addition to the lysimeter, also six soil moisture sensors (model CS650) and 2 meteorological stations were installed. The first results show recharge rates of natural precipitation ranging from 19 to 97%, depending on the meteorological conditions and the initial soil moisture. The lysimeter-measured rainfall generally exceeded the measurements of the tipping bucket. Also the contribution of the dew was detected by the lysimeter. A soil water model is currently being set up to simulate recharge, soil water movement, evaporation and percolation, as well as to quantify uncertainty and noise effects.