Low Rainfall Amounts Research Articles

Comparison of Thermal and Hydrotime Requirements for Seed Germination of Seven Stipa Species From Cool and Warm Habitats.

Temperature and water potential are two important environmental factors influencing germination and subsequent seedling establishment. Seed germination requirements vary with species and with the environment in which the seeds are produced. Stipa species dominate large areas of the Eurasian zonal vegetation, but comparisons of germination requirements between Stipa species from different habitats is limited. We investigated the effects of temperature and water potential on seed germination of S. grandis, S. purpurea, and S. penicillata from habitats with low temperatures and relatively abundant rainfall (cool habitats) and S. glareosa, S. breviflora, S. gobiea, and S. bungeana from habitats with relatively high temperatures and low amount of rainfall (warm habitats). Seeds of species from cool habitats had a higher base (T b), optimal (T o), and maximum (T c) temperature than those of species from warm habitats, except for the base temperature of S. purpurea. Response of six tested Stipa species to water potential differed among species but not between habitats. Median water potential for germination was lowest for S. bungeana, S. penicillata, and S. gobiea. There was a negative correlation between hydrotime constant (θ H) and base water potential for 50% of the seeds of all species to germinate (ψ b(50)). Germination time of seven Stipa species in response to temperature and water was well predicted by thermal time and hydrotime models. Results of the present study on germination of these seven species of Stipa may provide useful suggestions for grassland restoration in different habitats.

Implications of intra-seasonal climate variations on chlorophyll a fluorescence and biomass in winter barley breeding program

This study aimed to explore how ten selected winter barley genotypes responded to variations in environmental conditions during the growth season by using fast chlorophyll a fluorescence and normalized difference vegetation index (NDVI) at the booting, anthesis and early grain-filling stage. Lower amount of rainfall during the anthesis induced instability in the function of PSII, observed as the positive K-band in six and the positive L-band in seven genotypes. At grain filling, all genotypes displayed negative K- and L-bands, suggesting an increase of stability within PSII. The performance index increased from booting to grain filling in most genotypes. Chlorophyll a fluorescence parameters were incorporated into the partial least squares model as explanatory variables of NDVI. After a cross-validation, the model with four latent variables was chosen explaining 75.8% variance (r = 0.870) for NDVI. The principal component analyses showed two distinct types of the reaction of the barley genotypes to the mild drought stress at anthesis.

Application of a standardized precipitation index for mapping drought severity in an arid climate region, southeastern Iran

Drought is a recurring climate phenomenon causing many environmental and agricultural problems among others. To limit drought consequences, it is essential to monitor drought and implement efficient control measures. The aim of this study is to investigate the application of the Standardized Precipitation Index (SPI) for the 1-, 3-, 6-, 12-, 24-, and 48-month timescales for mapping the drought severity as an effective water management tool in an arid climate region. Calculations of the SPI were performed using historic records of monthly precipitation data of 50 stations over the Sistan and Baluchistan province, southeast of Iran. The majority of the SPI variants showed a moderate to strong spatial correlation with a spherical structure. In 1997, having a higher amount of rainfall, all areas across the province were in a wet or normal condition. In the years with a low rainfall amount (e.g., 2012), the western and southeastern parts of the province have been affected by different degrees of drought especially at the moderate timescales 6 and 12 months. The generated SPI maps identified the most vulnerable regions to drought over the province where government investments should be prioritized for an improved resiliency of the water management infrastructures and for designing a strategic crop management plan with less irrigation water demands.

Hydrologic response in the karstic and basaltic hydro-geological units of Lake Kinneret watershed

The hydrologic responses of two similar in size watersheds in the Lake Kinneret basin are examined: Karstic Hermon watershed and basaltic Meshushim watershed. The streamflow properties at these watersheds are different in their surface flow to baseflow ratio, runoff coefficients and response to extreme rainfall events. The HYdrological Model for Karst Environment (HYMKE) model, developed to simulate daily flow in karst formation, was modified to address the basaltic formation at the Meshushim watershed. Water fluxes simulations were used to compare the hydrologic processes between the watersheds. The twice-higher annual precipitation in the Hermon watershed, generates annual streamflow that is five times more than in the Meshushim. This amplification of the rainfall-streamflow ratio between the watersheds is because larger fraction of the rainfall is lost to evapotranspiration at the basaltic Meshushim watershed and larger portion of the rainfall percolates to the karstic aquifer through preferential flow and appear as baseflow at the Hermon watershed. During large rainfall events when soil water content is near saturation, lower rainfall amount over the Meshushim watershed generates larger peak flow than the Hermon watershed. In both watersheds, surface flow was generated only when the soil water content is at or near saturation conditions. The streamflow dependency on soil water content, suggests high sensitivity of streamflow generation to the intra-annual variability of precipitation. Understanding the hydrologic response of the different sources of Lake Kinneret improves the ability to forecast its inflow.

Large Scale Agricultural Investment and a Fragile Soil Paradox in Benishangul Gumuz Regional State: Organic Carbon Stock of Broadleaf and Deciduous Forests of Combretum_Terminalia Woodlands of Benishangul Gumuz Regional State, Western and Northwestern Ethiopia.

The organic carbon stock analysis was carried out in Broadleaf and Deciduous Forests of Benishangul Gumuz Regional State of Ethiopia with the objective of determining carbon stock that would be found in Broadleaf and Deciduous Forests of Benishangul Gumuz Regional State (BGRS). The assessment was conducted from 22nd September to 22nd 0ctober 2017. A total of 101 flowering plant species were sampled in 35 sample plots. Three vegetation cover types were identified: Grassland, Open Woodland and Closed woodland. Among the different habitat types in the area; namely: Closed Wood Land (CWL), Open Wood Land (OWL), Grass Land (GL) and Bare Land (BL). The maximum mean Total Carbon Stock Density (TCSD) was recorded from Closed wood land habitat with TCSD of 471 tons of carbon ha-1, followed by OWL, GL and BL with TCSD of 375.79, 118.75 and 47.92 tons of carbon ha-1 respectively. Since the area is located in lower altitude with low amount of rainfall per year and fire prone area, the mean total above ground carbon stock density of the study area which is 134.94 tons of carbon ha-1 is very low as compared to the other forest types. The anthropogenic factors (the human influence) on the woody vegetation particularly the annual burning of the vegetation does not allow a chance for the accumulation of carbon in the soil.

Drought Risks and Impacts on Ecosystems in Salahaddin Governorate

Environmental systems: are functional units of permanent life on Earth, the environment is a well-defined structure and dimensions have all the characteristics and standards of the systems are as a system consists of a group of elements such as land, water, air, energy and living creatures and this together constitutes an integrated unit characterized by continuity and equilibrium. Due to the continuous changes in the internal factors of the structure of this system, ecosystems in arid and semi-arid regions are highly sensitive to environmental variables such as extremes in climatic and soil characteristics, different terrain and depletion of water resources. As well as the role of the human factor as an influence, the indicators show that in many ways, including the decline of vegetation cover and the expansion of barren and desert areas and areas of salinization and weak economic systems, which creates a state of unbalance and imbalance in them. Comprehensive destruction of agricultural crops and increase their prices in the market, which leads to the creation of hotbeds of tension, especially for poor areas. The dominance of the study area due to the prevalence of the continental character resulting from the low amount of rainfall and fluctuations and the low relative humidity in the air and thermal extremes and water deficit make it one of the areas at risk of drought, which focuses on this study.

Organic carbon stock of broadleaf and deciduous forests of combretum_terminalia woodlands of benishangul gumuz regional state, western and northwestern Ethiopia

The organic carbon stock analysis was carried out in Broadleaf and Deciduous Forests of Benishangul Gumuz Regional State of Ethiopia with the following objective: determine carbon stock that would be found in Broadleaf and Deciduous Forests of Benishangul Gumuz Regional State (BGRS). The assessment was conducted from 22nd September to 22nd 0ctober 2017. A total of 101 flowering plant species were sampled in 35 sample plots. Three vegetation cover types were identified: Grassland, Open Woodland and Closed woodland. Among the different habitat types in the area; namely: Closed Wood Land (CWL), Open Wood Land (OWL), Grass Land (GL) and Bare Land (BL). The maximum mean Total Carbon Stock Density (TCSD) was recorded from closed wood land habitat with TCSD of 471 tons of carbon ha-1, followed by OWL, GL and BL with TCSD of 375.79, 118.75 and 47.92tons of carbon ha-1 respectively. Since the area is located in lower altitude with low amount of rainfall per year and fire prone area, the mean total above ground carbon stock density of the study area which is 134.94 tons of carbon ha-1 is very low as compared to the other forest types. The anthropogenic factors (the human influence) on the woody vegetation particularly the annual burning of the vegetation does not allow a chance for the accumulation of carbon in the soil.

Chemo-isotopes (18O &2H) signatures and HYSPLIT model application: Clues to the atmospheric moisture and air mass origins

The first ever systematic study on spatio-temporal variation of the chemo-isotopic compositions of the precipitation in Iran was carried out in a hydrological year (2016–2017) at 7 sites located in Bojnourd area, northeast of Iran. The main aims were to determine the moisture and air mass sources and, in particular, to evaluate the effect of atmospheric conditions on isotope compositions. The isotopic value of the precipitation fluctuates seasonally with higher values in summer and lower values in winter at the all sites. Stable isotope values of the precipitation samples within the local scale resulted a Bojnourd meteoric water line (BMWL): δD = 6.4 × δ18O+1.2 (R2 = 0.93, n = 75), with a lower slope and intercept than the global meteoric water line (GMWL) due to isotope kinetic fractionation effects during precipitation in semi-arid region with lower humidity. The air temperature can be suggested as the main controlling factor that impacts the stable isotope compositions of precipitation in the study area. The large rainfall events totally displayed the highest slope, intercept and d-excess values nearly similar to the snowfall samples, indicating the re-evaporation effects on the low rainfall amounts. Precipitations during summer season (Jun–August) with higher isotopes and lower d-excess values mainly originated from the polar and Caspian Sea air moistures. While, moisture contributing to high d-excess and low isotope precipitation during January was mainly transported by the Mediterranean air moisture. The air-mass trajectories that affect the precipitation in autumn (September–December) and spring (March–May) displayed multiple sources, originating from the polar, Mediterranean and Caspian Sea air moistures. Trajectory analysis by HYSPLIT modeling allowed the association of moisture sources with the isotopic compositions of the precipitation. Based on the sea salt contribution for Na+ and Cl−, a sea effect is recognized especially from Caspian Sea and Mediterranean region, despite the long distance at the present study. The correlation between EC and the ions indicate that ion compositions in the precipitation and atmosphere of the study area are mainly effected by dust of soil and sea salt and to some extent from secondary evaporation during rainfall. The hydrochemical investigations confirmed the air masses trajectories which resulted from the isotopic characteristics.

Effect of catchment lithology on dissolved inorganic carbon budgets in suburban streams of Baltimore, Maryland, during rainfall minima

Urbanization has the potential to affect riverine carbon exports, but relatively few studies have evaluated the potential effect of lithology on carbon fluxes in urban settings. To address this gap, four first-order streams in the Baltimore metropolitan area exhibiting different levels of impervious surfaces and catchment lithologies were examined for a span of ten weeks during a period of rainfall minima with the purpose of identifying sources and magnitudes of inorganic carbon transported by these streams during base flow conditions. Discharge, alkalinity, pH, temperature, and dissolved oxygen were measured in situ, whereas the carbon isotopic composition of dissolved inorganic carbon (DIC) was determined in the laboratory. Abundances of DIC and pCO2 were estimated from the collected data, revealing that the stream with an increased forest coverage and a calcareous catchment consistently had the highest values for DIC, pCO2, alkalinity, and stable isotope ratios. DIC yields for the four studied streams were relatively low, ranging from 2.6 to 21.8 mmol C/m2-yr, and calculated pCO2 evasion rates were some of the lowest recorded values in temperate and boreal regions, ranging from 184 to 6451 g C/day. These low values possibly resulted from the low rainfall amount that prevailed during the sampling period, which limited both the transfer of soil-derived DIC to the studied streams and the subsequent emission of CO2 to the atmosphere. Stable isotope data linearly correlated with DIC, and this relation could reflect the lithological control of inorganic carbon in the studied streams, with a 13C-enriched source of DIC probably representing the dissolution of calcareous metamorphic rocks and some contribution of soil-respired CO2 and with a 13C-depleted source interpreted to result from a predominant contribution of soil-respired CO2. Thus, our results point to the dominant effect of catchment lithology in regulating stream DIC budgets in the studied suburban streams during low discharge conditions.

Effect of grazing time and intensity on growth and yield of spring wheat (Triticum aestivum L.)

A simulated grazing field experiment was conducted to determine the effect of timing and intensity of grazing on the growth and yield of a mid-late maturing spring wheat (cv. Flanker) under different watering regimes, at Wagga Wagga in southeastern Australia. The experiment was a factorial design of watering regime and pasture “grazing” as factors, with three replications. The two watering regimes were rainfed (R) and supplemental irrigation (I). There were four simulated grazing treatments: no grazing, “crash” grazing by mowing to 5 cm height on 13 June (Cut1-5), “crash” grazing by mowing to 5 cm on 15 July (Cut2-5) and “clip” grazing by mowing to 15 cm height on 15 July (Cut2-15). The lowest dry matter (simulated grazing) was obtained from RCut1-5 (0.13 t ha−1) and the highest (0.86 t ha−1) was from ICut2-5. There was no significant difference (P<0.05) among the grain yields of the grazing treatments in the respective watering regimes. However, there was significant difference (P<0.05) between the grain yields of the rainfed (3.60 t ha−1) and irrigated (6.0 t ha−1) treatments. Under both watering regimes, the highest grain yield was obtained from the late “clip” grazings: 3.79 t ha−1 (RCut2-15) for rainfed and 6.47 t ha−1 (ICut2-15) for irrigated treatments. The lowest grain yield for the rainfed treatment was 3.26 t ha−1 (RCut1-5) and for the irrigated treatments, the lowest grain yield was 5.50 t ha−1 (ICut2-5). Harvest index (HI) was not significantly affected (P>0.05) by either the watering regime or grazing. Seed weight was significantly (P<0.05) affected both by the watering regime and grazing with the lowest value for 1000-seed weight of 30.05 g (RCut2-5) and the highest value of 38.00 g (ICut2-15). Water use efficiency was significantly (P<0.05) affected both by the watering regime and grazing with the lowest value of 9.94 kg ha−1 mm−1 (ICut2-5) and the highest value 13.43 kg ha−1 mm−1 (RCut2-5). By “crash” grazing late (just before stem elongation stage) to a height of 5 cm, a significantly higher (P<0.05) above ground dry matter can be grazed without significantly affecting the yield both in seasons with low amount of rainfall and high amount of rainfall (irrigated in this study) although in a wet season a slightly lower (15% lower) grain yield is obtained relative to “clip grazing” to 15 cm height. Grazing of mid-late maturing wheat cultivars has the potential to fill the feed gap without significantly affecting grain yield.

Predicting water erosion in arid lands using the GIS-based RUSLE model: A case study of Bedour catchment, central Tunisia

Abstract This study was conducted with a view to quantifying soil erosion in arid lands of Tunisia. To do this, we have opted to use the RUSLE model based on geographic information systems. By collecting data on rainfall, soils, vegetation, slopes and conservation practices separately as a layer and determining the pixel values for each of these factors, a quantified assessment of erosion in the basin is obtained. The data superposition and computing, following the model equations and protocol, allowed us to know the spatialized water erosion values at the pixel level. For the whole catchment, the study showed values oscillating between 0 and 163 Mgꞏha−1ꞏyear−1 with an average annual rate of 3 Mgꞏha−1ꞏyear−1. With such a low R (rainfall erosivity) factor (between 21.43 and 21.88 MJꞏmmꞏha–1ꞏh–1ꞏyear–1) itself related to low monthly and annual rainfall amounts, the region experiences locally very high annual erosion rates. Soil protection through conservation practices has saved the basin from even higher erosion. While plains cultivated and equipped with contour benches often suffer from low rates of erosion (less than 2 Mg·ha–1·year–1), unused slopes are neglected without protection, resulting in significantly high rates of erosion.

Heavy rainfall in Mediterranean cyclones, Part II: Water budget, precipitation efficiency and remote water sources

In this study, we use convection-permitting high resolution (3 km) simulations to quantify and analyse the water budget, precipitation efficiency and water sources of 100 intense Mediterranean cyclones. To this end, we calculate the water content, advection and microphysical processes of water vapour and rain water by implementing new diagnostics to the Weather Research and Forecasting (WRF) model. The 100 intense cyclones have been randomly selected from a 500 intense cyclones dataset, identified and tracked in an 11-year time period in part I of this study. Results are presented in a composite approach showing that most rainfall takes place to the north-east side of the cyclones, close to their centre. Rainfall location is concomitant to the area of horizontal moisture flux convergence and is quasi-equal to the amount of water vapour loss due to microphysical processes. Similar results were found regardless if cyclones produce high or low rainfall amounts. Vertical profiles of the water budget terms revealed deeper clouds for the cyclones producing high rainfall, consistent with higher values of vertical advection of both water vapour and rain water. Finally, cyclones were analysed with respect to their precipitation efficiency, i.e. the ratio between the rainwater produced in an atmospheric column and the consequent rainfall, and showed that cyclones tend to be more efficient when their rainfall production takes place over land. Therefore, there is a complex relation between water vapour advection, precipitation efficiency and rainfall which is discussed through the comparison of two tropical-like cyclones with two cyclones that produced low rainfall amounts. Finally, our analysis is complemented by applying a Lagrangian approach to all 100 cyclones in order to quantify the water vapour source regions that contribute to the cyclones’ rainfall due to local surface evaporation. Results showed that these regions are located over both the Atlantic and the Mediterranean, however we show that cyclones producing high rainfall are related with higher water transport from both the subtropical Atlantic and the Mediterranean Sea. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Application of Modified &amp;lt;i&amp;gt;MAR&amp;lt;/i&amp;gt; Model in Barnai River Basin, NW Bangladesh: A Performance Study

Present study aims to evaluate performance analysis of modified recharge well (RW) technique of the Managed aquifer Recharge (MAR) models for rain water from rooftop of office building and that of runoff water from Kharoil <i>Beel</i> (Swamp) harvesting approach in Barnai river basin, north-western part of Bangladesh. In the area, the lower amount of rainfall than country-wide average as well as less infiltration capacity of thick top clay layer lies above the potential aquifer at higher depth put constrain for groundwater resource development against its ever increasing demand day by day along with limited scope to conserve surface water in rivers, <i>Kharies</i> (canals), <i>Beels</i> etc. The performance of modified MAR model for recharge rate calculation with a goal to restore declining trend of groundwater level (GWL) are found good without any quality hazard. Moreover, for continuous operation and better performance of MAR model, regular monitoring and maintenance are necessary along with in-depth research activities to address the burning water scarcity for drinking and irrigation management issue as viable option in sustainable way.

Time-space characterization of droughts in the São Francisco river catchment using the Standard Precipitation Index and continuous wavelet transform

ABSTRACT This paper focuses on time-space characterization of drought conditions in the São Francisco River catchment, on the basis of wavelet analysis of Standardized Precipitation Index (SPI) time series. In order to improve SPI estimation, the procedures for regional analysis with L-moments were employed for defining statistically homogeneous regions. The continuous wavelet transform was then utilized for extracting time-frequency information from the resulting SPI time series in a multiresolution framework and for investigating possible teleconnections of these signals with those obtained from samples of the large-scale climate indexes ENSO and PDO. The use of regional frequency analysis with L-moments resulted in improvements in the estimation of SPI time series. It was observed that by aggregating regional information more reliable estimates of low frequency rainfall amounts were obtained. The wavelet analysis of climate indexes suggests that the more extreme dry periods in the study area are observed when the cold phase of both ENSO and the PDO coincides. While not constituting a strict cause effect relationship, it was clear that the more extreme droughts are consistently observed in this situation. However, further investigation is necessary for identifying particularities in rainfall patterns that are not associated to large-scale climate anomalies.

Quaternary sedimentary record in the northern Okinawa Trough indicates the tectonic control on depositional environment change

During the Quaternary, global sea level was characterized by large fluctuations in amplitude and increased frequency. However, the eastern marginal seas of China, especially the northern East China Sea and Yellow Sea did not experience large-scale transgression until the middle Pleistocene. The Zhe-Min (Zhejiang-Fujian) Uplift was an important barrier in the East China Sea preventing transgression of sea water into the northern marginal seas of China, but its Quaternary evolution is still poorly constrained. Here we present a thick sand layer record (the top age is ~416 ka) of the Integrated Ocean Drilling Program (IODP) Site U1428 from the northern Okinawa Trough to reconstruct the history of the Zhe-Min Uplift since the middle Pleistocene. Provenance analysis indicates that sediments from both sand and imbedded fine-grained calcareous-rich clay layers at the study site were mainly derived from the Yellow River, which for the first time indicates that the Yellow River sediments could influence the northern Okinawa Trough since at least the middle Pleistocene. Significant change of lithology at IODP Site U1428 at ~416 ka was attributed to the large-scale subsidence of the Zhe-Min Uplift, which is probably due to the rapid uplifting of Tibet during 0.52–0.38 Ma. Before ~416 ka, obstacle of the emersed Zhe-Min Uplift induced extremely severe reworking and promoted sand ridge formation in the shelf edge of southeastern Yellow Sea, and supplied sand sediments to the northern Okinawa Trough during transgression and high sea-level stages. After the subsidence of the Zhe-Min Uplift at ~416 ka, westward of tidal sand ridge and Yellow River mouth with the process of shelf transgressions favored fine-grained sediments input to the northern Okinawa Trough. Even during low sea-level stages, the flat terrain of the East Asian marginal sea shelf and low rainfall amount resulted in low discharge of Yellow River, and supplied fine-grained particles to the northern Okinawa Trough.

A centurial analysis of rainfall variability in Nigeria

This paper examines rainfall variability in Nigeria using monthly rainfall data from 1901 to 2012. This is necessary for planning and management of agriculture and water resource systems. Data for the study were retrieved from the portal archives of World Bank Climate Change Knowledge. Descriptive statistics, trend analysis, and seasonality index were employed in the study. Fluctuations across the months and years were respectively examined through MAKESENS® statistics and Seasonality Index. The result revealed minimum and maximum amounts of rainfall in January and August respectively. The Z and Q statistics indicate an upward trend and positive slope respectively but the null hypothesis of no trend is accepted only in November, December and January due to very low amount of rainfall. The highest maximum and minimum amount of rainfall occurred in July and August while the lowest maximum and minimum both took place in January but the years in which these sets of maximums and minimums happened each followed a zigzag pattern which connotes fluctuations in the amount of rainfall. The maximum, minimum and average seasonality indexes are 0.924, 0.706 and 0.779 respectively, which indicate seasonal and markedly seasonal with a long dry season. There is the need to harvest, store and treat excess water during the wet months for use in dry months. The study recommends that the ministry of water resources should adopt best practices to provide water for Nigerians during the long dry months.Keywords: Rainfall, climate variability, seasonality index, trend, water resources

The effects of rainfall regimes and terracing on runoff and erosion in the Three Gorges area, China.

Changes in natural rainfall regimes have taken place and are expected to become more pronounced in future decades. These changes are also likely to be accompanied by changes in crop management practices. The main purpose of this study was to analyze runoff and soil loss in relation to rainfall regimes and terracing in the Three Gorges area, China. Based on 10years of field observation and k-mean clusters, 101 rainfall events were grouped into three rainfall regimes. Rainfall regime I was the group of events with strong rainfall intensity, high frequency, and short duration. Rainfall regime III consisted of events with low intensity, long duration, and high rainfall amount. Rainfall regime II was the aggregation of events of high intensity and amount, and less frequent occurrence. The results showed that event runoff coefficients were not significantly different among rainfall regimes. However, the average soil erosion rates in rainfall regimes I and II were significantly higher than that in regime III. The average erosion rates under rainfall regimes I, II, and III were 21.6, 39.7, and 9.8gm-2, respectively. The effect of rainfall regime on soil erosion also was changed by terracing. On unterraced cropland, soil erosion rate in rainfall regime I is significantly higher than that in regime III. However, the situation did not exist in unterraced orchard. Terracing significantly reduced runoff and soil erosion, and compensated the effects of rainfall regime on soil erosion, which indicated that runoff and erosion in terraced system may be little influenced by climate change. Based on these results, it was suggested more attention should be paid to the timing of rainfall events in relation to crop development and the high erosion on unterraced citrus orchard to control soil erosion in this area.

Domestic water demand challenges in Qatar

Qatar is an arid country with limited water resources due to the low amount of rainfall it receives. With no surface water and an average annual rainfall of 80 mm per year, Qatar relies upon desalination to meet the increasing domestic water demand. The average annual rainfall recharge is around 60 million m3, whereas the total groundwater abstraction is 250 million m3 per year. As a result, groundwater level drops dramatically, thereby inducing brackish water upconing and saline water intrusion. Desalination provides 99% of domestic water demand, which increases continuously as a result of the influx of migrants into the country. The current capacity of desalination plants in Qatar is around 540 million m3 per year. Around 30% of this volume is being lost as a result of leakage in the water system network, and the rest is used for domestic purposes. This paper discusses three different scenarios of water demand until the year 2040. The results of these scenarios show water demand will vary between 516 and 2718 million m3 in the year 2040, depending upon the various trends in population growth, and assuming the current per capita of 500 l/day. The results of this study highlight the need for water rationing and conservation and may help the planners of future water demand.

Impact of multi-day rainfall events on surface roughness and physical crusting of very fine soils

Soil surface roughness (SSR), a description of the micro-relief of soils, affects the surface storage capacity of soils, influences the threshold flow for wind and water erosion and determines interactions and feedback processes between the terrestrial and atmospheric systems at a range of scales. Rainfall is an important determinant of SSR as it can cause the dislocation, reorientation and packing of soil particles and may result in the formation of physical soil crusts which can, in turn, affect the roughness and hydrological properties of soils. This paper describes an experiment to investigate the impact of a multi-day rainfall event on the SSR and physical crusting of very fine soils with low organic matter content, typical of a semi-arid environment. Changes in SSR are quantified using geostatistically-derived indicators calculated from semivariogram analysis of high resolution laser scans of the soil surface captured at a horizontal resolution of 78μm (0.078mm) and a vertical resolution of 12μm (0.012mm). Application of 2mm, 5mm and 2mm of rainfall each separated by a 24h drying period resulted in soils developing a structural two-layered ‘sieving’ crust characterised by a sandy micro-layer at the surface overlying a thin seal of finer particles. Analysis of the geostatistics and soil characteristics (e.g. texture, surface resistance, infiltration rate) suggests that at this scale of enquiry, and for low rainfall amounts, both the vertical and horizontal components of SSR are determined by raindrop impact rather than aggregate breakdown. This is likely due to the very fine nature of the soils and the low rainfall amounts applied.

Heavy rainfall in Mediterranean cyclones. Part I: contribution of deep convection and warm conveyor belt

In this study, we provide an insight to the role of deep convection (DC) and the warm conveyor belt (WCB) as leading processes to Mediterranean cyclones’ heavy rainfall. To this end, we use reanalysis data, lighting and satellite observations to quantify the relative contribution of DC and the WCB to cyclone rainfall, as well as to analyse the spatial and temporal variability of these processes with respect to the cyclone centre and life cycle. Results for the period 2005–2015 show that the relationship between cyclone rainfall and intensity has high variability and demonstrate that even intense cyclones may produce low rainfall amounts. However, when considering rainfall averages for cyclone intensity bins, a linear relationship was found. We focus on the 500 most intense tracked cyclones (responsible for about 40–50% of the total 11-year Mediterranean rainfall) and distinguish between the ones producing high and low rainfall amounts. DC and the WCB are found to be the main cause of rainfall for the former (producing up to 70% of cyclone rainfall), while, for the latter, DC and the WCB play a secondary role (producing up to 50% of rainfall). Further analysis showed that rainfall due to DC tends to occur close to the cyclones’ centre and to their eastern sides, while the WCBs tend to produce rainfall towards the northeast. In fact, about 30% of rainfall produced by DC overlaps with rainfall produced by WCBs but this represents only about 8% of rainfall produced by WCBs. This suggests that a considerable percentage of DC is associated with embedded convection in WCBs. Finally, DC was found to be able to produce higher rain rates than WCBs, exceeding 50 mm in 3-h accumulated rainfall compared to a maximum of the order of 40 mm for WCBs. Our results demonstrate in a climatological framework the relationship between cyclone intensity and processes that lead to heavy rainfall, one of the most prominent environmental risks in the Mediterranean. Therefore, we set perspectives for a deeper analysis of the favourable atmospheric conditions that yield high impact weather.