Rainy Years Research Articles

Investigating the impact of urban development on the activation of a paleolandslide. A case study from Pissouri, Cyprus

The present study investigates the reactivation of a paleolandslide due to the expansion of a community in an area covered by plastic Pliocene marls in the southwestern part of Cyprus. The landslide, which takes place in an area with gently sloping ground and relatively shallow water table, affects more than 100 residential buildings. In the context of the study, building damages and ground surface ruptures were mapped through field work campaigns. Remote sensing data from InSAR (Interferometric Synthetic Aperture Radar) analysis were evaluated in conjunction with available geological, geotechnical and hydrogeological data. Subsequently, the landslide was backanalyzed using the finite element method to examine possible failure mechanism scenarios and shed light on the influence of potential triggering factors. The results indicate that the paleolandslide has been almost fully reactivated, with the main cause of the reactivation being the rising of the phreatic water table due to long-term discharges of wastewater through the absorption pits of the residential developments. The water table rise was further amplified by rainwater infiltration during rainy years. According to the backanalysis results, the slip surface follows the bedding planes of weak marl horizons with residual friction angle of the order of 10°.

Spatiotemporal Rainfall Analysis of El Nino, Neutral and La Nina Years Across Belg and Kiremt Seasons Over Oromia Region Ethiopia

ENSO is the primary natural hazard that contributes to food insecurity and poverty. It has been influencing countries’ climatic regimes for decades, bringing frequent floods and droughts. There is limited knowledge on El Niño and La Niña occurrences that affect agricultural activities in the Oromia Region and occur during the Belg and Kiremt seasons when rainfall is distributed. Evaluating the spatiotemporal rainfall performance of ENSO years spanning Belg and Kiremt seasons rainfall distribution over the research area is the primary goal. For the study’s spatial and temporal analyses, satellite rainfall data from 1981 to 2021 was obtained from CHG-UCSB and https://earlywarning.usgs.gov/fews/ewx_lite/index.html, respectively. The study’s findings demonstrated a substantial association between the Belg and Kiremt seasons spanning El Niño and La Niña periods, with a range of correlation values indicating a weak, moderate, and strong relationship. Because of the spatial and temporal dynamics of this study area, ENSO phases indicate that exceptionally dry years are probably linked to El Niño occurrences in the region, whereas extraordinarily rainy years are likely linked to La Niña events. Seasonal rainfall performance and rainfall variability are impacted by ENSO events and other regional systems, with both positive and negative effects observed throughout the research area. In addition to examining the ENSO (Neutral, El Niño, and La Niña) that have a major impact on the seasonal rainfall performances in the Oromia region, this study also looked at the water availability, yield production, pastoralist and agro-pastoralist activities, and water availability. In summary, the results of this research can help us better understand the mechanisms underlying regional ENSO events and their causes, which will be especially useful when future climate conditions change.

Co-Occurrence of Fusarium and Alternaria Metabolites in Brewing Barley Monitored during Two Consecutive Years (2019-2020).

Known mycotoxins have been investigated for years. They have been included in legislation and are meticulously controlled in most cereals, cereal-related products, and raw materials of animal origin. However, there are still mycotoxins that need to be addressed by regulations and subsequently are not monitored but can still occur in relatively high concentrations. This research aimed to assess the occurrence of common Fusarium mycotoxins in hulled barley. Samples of hulled barley were treated in the field with two protective treatments, alongside a control sample sans treatment. Furthermore, we aimed to assess the occurrence of Alternaria mycotoxins in the chosen samples. The results have shown that Fusarium mycotoxins were mostly determined by climatic conditions (no mycotoxins in 2020, except siccanol). Most interesting was the appearance of infectopyron, an Alternaria toxin that was detected in all samples in 2019 and in the majority of samples in 2020. The highest concentration was detected in 2019 in hulled barley with 536 µg/kg, while in 2020, the highest concentration of this mycotoxin reached 350 µg/kg. These findings depict the need for further research on food safety regarding mycotoxins, and the need for additional changes in legislation. This investigation shows that fungicide application in rainy years cannot efficiently suppress mycotoxin production. Additionally, even in dry years, some of the mycotoxins not involved in legislation, such as infectopyron and siccanol, do not respond to the application of fungicides.

The Impact of Crop Year and Crop Density on the Production of Sunflower in Site-Specific Precision Farming in Hungary

Sunflower is considered a plant with extraordinary adaptability. However, the conditions of growing sunflower function as a limiting factor in its production. The hybrids used in production tolerate weather variability to a different level and utilise the nutrient and water resources of the soil, while the yield is also affected by the number of plants per hectare. In this study, the authors attempted to observe the environmental effects influencing sunflower cultivation, the heterogeneous productivity zones of the given production site and the correlation of the number of seeding plants used under various farm practices. The average rainfall of 2021 and the dry weather of 2022 created suitable conditions for examining the yearly weather effect. In the selected experimental areas, three distinguishable zones were defined in terms of productivity. In each productivity zone, three crop density steps were used in four replicates. Based on the performed comparative tests, the rainy year of 2021 resulted higher yield than the drier year of 2022 in the average- and high productivity zones, while in the low-productivity zone, higher yields were harvested under the drier conditions of 2022 than in the rainy year of 2021. In 2021, with the improvement in productivity, the obtained yield was also higher. However, in 2022, this clarity could not be demonstrated. In the zones with low productivity, identical yield results were observed in both weather conditions. Based on the examination of the obtained results, it was shown that the effect of weather conditions and the given number of plants have a smaller influence on the yield results of low-productivity zones, while these factors have a greater influence on the yields of high-productivity zones.

Bathymetric Map Production of Therthar Depression Basin and Water Storage Volume Estimation

Water crisis, drought, and desertification are prominent environmental issues facing many countries and threaten their sustainable development. Therthar depression basin in Iraq was selected as a study area. A new approach was adapted in producing a bathymetric map by merging contours derived from both topographic maps and digital elevation models using ArcGIS applications. Water storage volumes were estimated from 2017 to the end of 2023 using the trapezoidal rule. The results demonstrate that the maximum water storage volume was 80% of the total storage capacity in 2019. In 2021, this percent began to decrease significantly as a result of climatic changes until reached a dead storage about 40% in 2023. Large surface area of Therthar depression leads to increased evaporation and infiltration rates. The water consumption exceeded the incoming water storage by 5.292 billion cubic meters (bcm) in May and 13.127 bcm in October, between 2017 and 2023. The comparison between the estimated and actual live storage volumes resulted a root mean square error of 0.534 m and a coefficient of determination (R2) equals 0.871. However, to award off flood risks in rainy years, the study proposes increasing Therthar depression design elevation to 67 m rather than 65 m in proportion to Therthar arranger gate level.

Can we identify tipping points of resilience loss in Mediterranean rangelands under increased summer drought?

Mediterranean ecosystems are predicted to undergo longer and more intense summer droughts. The mechanisms underlying the response of herbaceous communities to such drier environments should be investigated to identify the resilience thresholds of Mediterranean rangelands. A 5-year experiment was conducted in deep and shallow soil rangelands of southern France. A rainout shelter for 75 days in summer imposed drier and warmer conditions. Total soil water content was measured monthly to model available daily soil water. Aboveground net primary production (ANPP), forage quality, and the proportion of graminoids in ANPP were measured in spring and autumn. Plant senescence and plant cover were assessed in summer and spring, respectively. The experimental years were among the driest ever recorded at the site. Therefore, manipulated summer droughts were drier than long-term ambient conditions. Interactions between treatment, community type, and experimental year were found for most variables. In shallow soil communities, spring plant cover decreased markedly with time. This legacy effect, driven by summer plant mortality and the loss of perennial graminoids, led to an abrupt loss of resilience when the extreme water stress index exceeded 37 mm 10 day-1, characterized by a reduction of spring plant cover below 50% and a decreased ANPP in rainy years. Conversely, the ANPP of deep soil communities remained unaffected by increased summer drought, although the presence of graminoids increased and forage nutritive value decreased. This study highlights the role of the soil water reserve of Mediterranean plant communities in modulating ecosystem responses to chronically intensified summer drought. Communities on deep soils were resilient, but communities on shallow soils showed a progressive, rapid, and intense degradation associated with a loss of resilience capacity. Notably, indexes of extreme stress were a better indicator of tipping points than indexes of integrated annual stress. Considering the role of soil water availability in other herbaceous ecosystems should improve the ability to predict the resilience of plant communities under climate change.

Determining Factors and Economic Injury Levels for Sphenophorus levis for Chemical and Biological Control in Irrigated and Non-irrigated Sugarcane Crops.

Globally, people use sugarcane (Saccharum officinarum) to produce sugar and ethanol. Rainfed or irrigated sugarcane agricultural systems are available. Among the pests affecting this crop, the weevil Sphenophorus levis, Vaurie 1978 (Coleoptera: Curculionidae), is increasingly becoming a significant threat in southern South America. Sphenophorus levis populations are controlled using chemical or biological measures. Control decisions hinge upon the economic injury level (EIL). The EIL delineates the pest density that results in financial losses for producers. This study aims to determine the EIL for S. levis, considering the factors favoring this insect pest and chemical and biological control methods in rainfed and irrigated systems. The intensity of S. levis attacks was monitored in commercial sugarcane plantations over four years in João Pinheiro, Minas Gerais, Brazil. Sampling occurred in a 50 × 50 × 30-cm-deep trench dug in the soil surrounding the sugarcane clump. The total number of stumps in the clump, including those attacked by S. levis, was tallied. The EILs for this pest were 5.93% and 4.85% of targeted stumps for chemical control in rainfed and irrigated crops, respectively. Biological control in sugarcane plots resulted in an EIL of 4.15% and 3.40% for stumps attacked in rainfed and irrigated crops, respectively. Pest attacks were more severe during rainy years and in older sugarcane crops. The EIL values determined in this study could inform integrated pest management programs for sugarcane crops.

Interannual Variability of Water and Heat Fluxes in a Woodland Savanna (Cerrado) in Southeastern Brazil: Effects of Severe Drought and Soil Moisture

The Brazilian Cerrado biome is known for its high biodiversity, and the role of groundwater recharge and climate regulation. Anthropogenic influence has harmed the biome, emphasizing the need for science to understand its response to climate and reconcile economic exploration with preservation. Our work aimed to evaluate the seasonal and interannual variability of the surface energy balance in a woodland savanna (Cerrado) ecosystem in southeastern Brazil over a period of 19 years, from 2001 to 2019. Using field micrometeorological measurements, we examined the variation in soil moisture and studied its impact on the temporal pattern of energy fluxes to distinguish the effects during rainy years compared to a severe drought spell. The soil moisture measures used two independent instruments, cosmic ray neutron sensor CRNS, and FDR at different depths. The measures were taken at the Pé de Gigante (PEG) site, in a region of well-defined seasonality with the dry season in winter and a hot/humid season in summer. We gap-filled the energy flux measurements with a calibrated biophysical model (SiB2). The long-term averages for air temperature and precipitation were 22.5 °C and 1309 mm/year, respectively. The net radiation (Rn) was 142 W/m2, the evapotranspiration (ET) and sensible heat flux (H) were 3.4 mm/d and 52 W/m2, respectively. Soil moisture was marked by a pronounced negative anomaly in the 2014 year, which caused an increase in the Bowen ratio and a decrease in Evaporative fraction, that lasted until the following year 2015 during the dry season, despite the severe meteorological drought of 2013/2014 already ending, which was corroborated by the two independent measurements. The results showed the remarkable influence of precipitation and soil moisture on the interannual variability of the energy balance in this Cerrado ecosystem, aiding in understanding how it responds to strong climate disturbances.

Statistical downscaling of future temperature and precipitation projections in Iraq under climate change scenarios

The research was aimed to; (i) study the observed climate in Iraq from 1971 to 2021 for annually, monthly and seasonally averages of temperature and precipitation for nine meteorological stations; ii) produce RCP4.5 and RCP8.5 scenarios for Iraq region under historical (1900–2005) and future periods (2006–2100) for temperature and precipitation using NCAR-CCSM4 database; and iii) examine the anomaly for near future (2025–2034) and medium future (2050–2059), related to 1986–2005. To evaluate the performance of the monthly averages of temperature and precipitation, three bias correction techniques i.e., Delta, Empirical Quantile Mapping, and Quantile Mapping were applied to nine metrological stations. The results revealed that the Delta is the most efficient method to bias correction for the monthly averages related to temperature and precipitation. The annual average temperature increased from 22.9 C° in 2006, based on both RCP4.5 and RCP8.5, to 24.0 C° and 27.2 C°, respectively, and the anomaly increased from −0.9 C° and −1.9 C° in 2006, to 0.6 C° and 2.4 C°. The precipitation annual and winter month's averages under RCP4.5 and RCP8.5 from 2006 to 2100, 2020–2039 and 2040–2059 showed that southwest region in Iraq (Basra, Missan and Thi-Qar provinces) had more drought and low precipitation than the other regions. From 2029 to 2034 and 2050–2054, rainy years have been predicted, using RCP4.5. Based on RCP.8.5, from 2025 to 2034 and 2050–2055, should witness rainy years, followed by a drought period. The results expected to support decision-makers in incorporating a national initiative to break down social barriers, encourage growth prospects, particularly in southern Iraq.

Effect of rainfall in shaping microbial community during Microcystis bloom in Nakdong River, Korea

Various environmental factors play a role in the formation and collapse of Microcystis blooms. This study investigates the impact of heavy rainfall on cyanobacterial abundance, microbial community composition, and functional dynamics in the Nakdong River, South Korea, during typical and exceptionally rainy years. The results reveal distinct responses to rainfall variations, particularly in cyanobacterial dominance and physicochemical characteristics. In 2020, characterized by unprecedented rainfall from mid-July to August, Microcystis blooms were interrupted significantly, exhibiting lower cell densities and decreased water temperature, compared to normal bloom patterns in 2019. Moreover, microbial community composition varied, with increases in Gammaproteobacteria and notably in genera of Limnohabitans and Fluviicola. These alterations in environmental conditions and bacterial community were similar to those of the post-bloom period in late September 2019. It shows that heavy rainfall during summer leads to changes in environmental factors, consequently causing shifts in bacterial communities akin to those observed during the autumn-specific post-bloom period in typical years. These changes also accompany shifts in bacterial functions, primarily involved in the degradation of organic matter such as amino acids, fatty acids, and terpenoids, which are assumed to have been released due to the significant collapse of cyanobacteria. Our results demonstrate that heavy rainfall in early summer induces changes in the environmental factors and subsequently microbial communities and their functions, similar to those of the post-bloom period in autumn, leading to the earlier breakdown of Microcystis blooms.

Effect of Different Nitrogen Levels on Water and Nitrate Distribution in Aeolian Sandy Soil under Drip Irrigation

Understanding the distribution of water and nitrate nitrogen in the soil profile is crucial for the reasonable operation of fertigation, and it is also fundamental for controlling and regulating nitrate nitrogen in the root zone, thereby meeting a crop’s requirements. The application rates of fertilizer and water directly influence this distribution of water and nitrate nitrogen. However, the effects in Aeolian sandy soil, a type of developing soil bordering deserts, remain ambiguous. In this study, field experiments for different drip fertigation treatments in Aeolian sandy soil were conducted to investigate the soil water distribution, as well as that of nitrate nitrogen. A completely randomized experimental design was implemented, encompassing three levels of irrigation amount: low (W1), medium (W2), and high (W3), and three levels of nitrogen application rate: low (F1), medium (F2), high (F3). After the completion of each irrigation treatment, soil samples were extracted at 10–20 cm intervals. The soil water and nitrate nitrogen contents in the profiles of these samples were measured. The experimental results revealed that increasing the nitrogen application rate facilitated the retention of greater amounts of water and nitrate nitrogen in the soil profile. However, with an increase in the nitrogen application rate, both soil water and nitrate nitrogen exhibited a radial tendency to move away from the drip emitter. Some moved upward and accumulated in surface soil near a ridge furrow, while some moved downward and remained in a deeper area approximately 30 cm horizontally from the emitter at depths of 40–60 cm. The uniformity of the water distribution decreased with increasing nitrogen application under low water conditions, with a reversal of this trend observed in medium and high water treatments. The effect of nitrogen application level on the uniformity of the nitrate nitrogen distribution was not significant. There was no significant correlation between the average soil water content and nitrate nitrogen content along the horizontal direction, however, a positive correlation existed in the vertical direction. In the whole profile, increasing the nitrogen application enhanced the correlation under low water conditions, but under medium and high water conditions, this trend was the opposite. This implies that, to avoid nitrate nitrogen leaching or limiting in a specific area, a moderate nitrogen application level is advisable. Under low water conditions, nitrogen application showed a positive effect on the nitrate nitrogen content, and a higher application is recommended. In cases of substantial water irrigation or rainy years, the nitrogen application rate should be decreased.

Effect of rainfall parameters on soil erosion in Chwalimski Brook catchment, NW Poland

Soil erosion by water is one of the most important factors affecting contemporary landscape changes within the lowland geoecosystems in Central Europe. Soil erosion mainly depends on rainfall (especially its intensity and erosivity), length of slope and its inclination, type of cultivation and usage of the land, antierosion treatments, and susceptibility of soils to erosion. The main goal of this research was to evaluate the impact of rainfall on soil erosion processes. This was realized by stationery observations and quantitative research conducted within the Chwalimski Brook catchment (NW Poland) since the early 90s. Additionally, the rainfall characteristics such as intensity, kinetic energy, and erosivity (represented by the rainfall erosivity indices EI5, EI10, EI15, EI20, EI30 and EI60) were computed. The presented results contain data on runoff, soil loss, and rainfall collected at a testing plot over 16 years (2001–2016 hydrological years). Annual rainfall erosivity (EI30) ranged from 144.7 to 782.1 MJ mm ha−1 h−1, precipitation totals varied from 524.9 to 919.7 mm, and soil loss ranged from 0.074 to 4.471 kg m−2. The greatest rates of soil loss were established in the most rainy years, although significant soil loss also occurred in below-average rainfall years, such as in 2013 and 2014. Consequently, the achieved results show that annual soil erosion primarily depends on individual rainfall and erosive events. Hence, the magnitude of soil erosion cannot be solely estimated based on the rainfall totals, but it is also necessary to consider the intensity and erosivity of each rainfall event.

Rainfall variability increased with warming in northern Queensland, Australia, over the past 280 years

Floods and droughts are hydrological extremes that impact ecosystems, agriculture, and human well-being. These extremes are expected to intensify in a warmer world, although many regions lack the observations needed to place current trends in the context of long-term variability. Here we present a new multi-century record of tropical rainfall based on a multi-proxy approach from northern Great Barrier Reef coral. The robust calibration with instrumental rainfall allows us to quantitatively estimate summer rainfall in northern Queensland back to 1746 CE. We find that as global climate warmed, wet-season rainfall in this region has increased by ~10% since 1750 and the standard deviation (21-yr 1-σ) of wet-season rainfall more than doubled, as rainy years became much wetter, while dry years remained dry. Reconstructed rainfall correlates with El Niño indices and the link to Pacific temperature variability has strengthened as climate warmed, consistent with expected intensification of La Niña-related rainfall.

Effects of Climate and Weeds on the Establishment of Thyme-Based Living Mulch Systems in Drylands of Cyprus

Backround: Mulching systems are at the spotlight of sustainable soil management as nature-based solutions for combating desertification.
 Aims: We tested how living mulch systems based on rainfed Thymbra capitata [(L.) Cav.], can be established under different pressure from drought and weeds in dryland carob plantations.
 Study design: 10 thyme plots in semi-arid climate (SKR); 11 plots in arid climate (VRY); different weed competition intensity (60 thymes per plot).
 Place and Duration of the Study: South-eastern Cyprus, between December 2019 and 2022.
 Methodology: Survival and soil cover for 1260 T. capitata seedlings (3-5 cm tall, 16 seedlings per m2) was assessed at the end of 3 dry seasons (d.s.) together with weed community composition, weed abundance (w.a.) and biomass. Climate data and De Martone’s Aridity Index (DMAI) were used to assess drought severity.
 Results: Around 80% of the thymes survived at the end of the first d.s, that followed a very rainy year (ca. 600 mm annual precipitation; P; ca. +50% than normal; ca. 19 DMAI). Thyme survival appeared unaffected by w.a. in both sites. After a severe drought that occurred the second year (ca. 300 mm P; ca. -22% than normal; ca. 9.5 DMAI) thyme survival rates dropped at the end of the d.s. to ca. 20% at the site with 3 times higher w.a./ biomass (mostly from Avena sp.). However, they were unaffected under low w.a. creating a 29% soil cover (vs.7% in VRY). These results remained till the end of the third d.s.
 Conclusions: To combat desertification and drought intensification under climatic change, rainfed T. capitata as living mulch appears unaffected by weeds during wet years, or in very dry years under low w.a. However, under high w.a., a weed management system is required if climate is arid.

Recent Tangible Natural Variability of Monsoonal Orographic Rainfall in the Eastern Himalayas

AbstractHimalayas hydroclimate is a lifeline for South Asia's most densely populated region. Every year, flooding in the Himalayan rivers is usual during summer monsoon, which impacts millions of inhabitants of the Himalayas and downstream regions. Recent studies demonstrate the role of melting glaciers and snow in the context of global warming, along with monsoonal rain causing recurrent floods. Here, we highlight the natural variability in the eastern Himalayan hydroclimate over the last 43 years (1979–2021). We found extreme monsoonal rainy years with six dry years and seven wet years after removing the climate change signal. Monsoon rainfall is a significant contributor, and melting snow is not a potential contributor to these anomalous extreme years. The variability of Himalayan monsoonal rainfall is strongly regulated by local monsoonal Hadley circulation associated with tropical sea surface temperature. Our findings demonstrate mechanisms associated with Himalayan wet and dry monsoon. Atmospheric dynamics are attributed as the primary modulating factor, influencing local thermodynamics through moist processes. The insights provided in this study underscore the impact of natural variability‐driven challenging events that could be predictable. Thus, this mechanism could improve the predictability of the Himalayas floods.

Modeling the Effects of Local Atmospheric Conditions on the Thermodynamics of Sobradinho Lake, Northeast Brazil

The objective of this work was to study climate variability and its impacts on the temperature of Sobradinho Lake in Northeast Brazil. Surface weather station data and lake measurements were used in this study. The model applied in this work is FLake, which is a one-dimensional model used to simulate the vertical temperature profile of freshwater lakes. First, the climate variability around Sobradinho Lake was analyzed. Observations showed a reduction in precipitation during 1991–2020 compared to 1981–2010. To study climate variability impacts on Sobradinho Lake, the years 2013, 2015, and 2020 were selected to characterize normal, dry, and rainy years, respectively. In addition, the months of January, April, July, and October were analyzed for rainy months, rainy–dry transitions, dry months, and dry–rainy transitions. Dry years showed higher incoming solar radiation at the surface and, consequently, higher 2 m air temperatures. A characteristic of the normal years was more intense surface winds. October presented the highest incoming solar radiation, the highest air temperature, and the most intense winds at the surface. The lowest incoming solar radiation at the surface was observed in January, and the lightest wind was observed in April. To assess the effects of these atmospheric conditions on the thermodynamics of Sobradinho Lake, the FLake model was forced using station observation data. The thermal amplitude of the lake surface temperature (LST) varied by less than 1 °C during the four months. This result was validated against surface lake observations. FLake was able to accurately reproduce the diurnal cycle variation in sensible heat fluxes (H), latent heat fluxes, and momentum fluxes. The sensible heat flux depends directly on the difference between the LST and the air temperature. During daytime, however, Flake simulated negative values of H, and during nighttime, positive values. The highest values of latent heat flux were simulated during the day, with the maximum value was simulated at 12:00 noon. The momentum flux simulated a similar pattern, with the maximum values simulated during the day and the minimum values during the night. The FLake model also simulated the deepest mixing layer in the months of July and October. However, our results have limitations due to the lack of observed data to validate the simulations.

Квантильный анализ плотности сложения и пористости целинных серых лесных почв юга Тюменской области

Statistical processing of a large array of data on the density of addition and total porosity of virgin gray forest soils in the south of the Tyumen region was performed. Quantile analysis (boxplot diagrams) was used to estimate the variability of values. It is established that the type of gray forest soils has relatively favorable agrophysical properties. The average density of the humus horizon (A1) in all three subtypes has values that fall within the range of the "optimum" of most agricultural crops. The illuvial horizon of light gray and actually gray forest soils is compacted, therefore, when these soils are introduced into arable land in rainy years, there is a high probability of violation of aeration and surface waterlogging. Keywords: GRAY FOREST SOILS, ADDITION DENSITY, POROSITY, QUANTILE ANALYSIS, BOXPLOT DIAGRAM

Temporal and lake-specific variations in oxygen and hydrogen stable isotopes in a boreal lake-chain during two hydrologically differing years

ABSTRACT Hydrogen and oxygen stable isotope mass ratios (δ2H and δ18O) are conservative tracers that reflect hydrological conditions of watersheds and lakes, information that can be used for water budgets, such as estimating nutrient loading from the catchments and direct and indirect effects of climate change on waterbodies. We measured δ2H and δ18O values and estimated water mass balances over 2 hydrologically differing years in a chain of 10 boreal lakes. During a warm and dry summer, evaporative loss enriched the isotope values at lake surfaces. Thus, in lakes that were thermally stratified during summer, the isotope values differed distinctively between epilimnion and hypolimnion. During the following rainy summer, the within-lake variation of isotope values was much lower with no clear trend, presumably a result of a more unstable water column and faster water throughflow in the lake chain. After autumnal mixing the lake δ18O values were strongly correlated with lake area and proportion of inland waters of the catchment area. The interannual within-lake difference was then ∼1‰, indicating differences in evaporation. Isotope mass balance (IMB) calculations and those based on lake temperature and hydrological measurements in the nearby region yielded similar results for the rainy ice-free period. Presumably, prerequisites of steady-state conditions for IMB were better met in the rainy year than during the previous drier year. For some lakes the results suggested remarkable volumes of groundwater inflow, whose role in boreal lake water budgets deserves more attention in future studies.

SPATIO-TEMPORAL ANALYSIS OF THE GROMBALIA AQUIFER DYNAMICS--NORTHERN EAST OF TUNISIA

Aquifer maps are key tools for water resources management, and allow to characterize a water table distribution and variability. The Grombalia plain in the northeast part of Tunisia was studied to identify the origin of groundwater recharge and to specify the type of recharge in the whole study area. It aims to investigate the impact of recharge schemes on the piezometric evolution of the water table. Furthermore, the purpose is to investigate the origin and dominant factor of the recharge. The methodology of this work includes two methods of analysis of the dynamics of the piezometric heads of this aquifer, namely the interpretation of piezometric maps for an evaluation of the spatial evolution and the study of piezometric sections. Both methods allow to distinguish between the different types of recharge, show which recharge sources is the most important in supplying the groundwater. In addition, they permit to analyze in detail the piezometric evolution and the impact of the various hydraulic structures on the piezometry. Without forgetting the naturel recharge coming directly from the soil surface and depending on the permeability, there is another natural recharge which comes from flooding areas. In Grombalia groundwater, this natural recharge occurs mainly at Wadi Ejjorf, Wadi Sidi Toumi and Wadi Ejdida sites. This recharge is accented for rainy years and mainly after flooding events. This study shows the picks at all the recharge sites between 1999 and 2009. However, an overexploitation of the aquifer was observed in Soliman-Fondok Jedid, Boucharray, Bou Argoub, which presented local depression zones. The used methodologies are very important tool to choose the best recharge site and allow to adjust the hydrodynamic models. In fact, there is an urgent need for assessing various aspects of ground water resources through a process of systematic data collection, analysis and synthesis.

Optimizing Rice Irrigation Strategies to Maximize Water Productivity: A Simulation Study Using AquaCrop Model for the Yanyun Irrigation District, Yangzhou, China

The AquaCrop model is used to predict rice yield in response to different irrigation management in the Yanyun irrigation area in Yangzhou, China, and the constraints to rice production were identified to maximize water productivity based on model simulations. The model was calibrated by comparing measured and predicted canopy cover (CC), yield, and soil water content during the growing season in 2018. The results showed that, for CC simulations, R2 was 0.99, RMSE was 3.6%, and NRMSE was 5.3%; for Biomass simulation, RMSE was 0.50 t/ha, and NRMSE was 5.3%. Different irrigation strategies were analyzed for a long-term simulation period from 1955 to 2014. The simulated rice yield increased rapidly as irrigation demand increased initially, and then gradually stabilized. The simulated rice yield fluctuated in the different years. The Pearson type-III model method was used to identify different hydrological years of wet, normal, and dry years. The analysis identified the wet year as 1991, normal year as 1981, and dry year as 1966. In the different rainfall years (1991, 1981, and 1966) water use efficiency (WUE), water productivity (WPet), and irrigation water productivity (IWP) were utilized to determine the irrigation strategy. The predicted highest WPet in the wet year was 1.77kg m−3, while the lowest WPet in the dry year was 1.13 kg m−3. The highest IWP was 19.78 kg m−3 in the wet year, and 9.32 kg m−3 in the normal year; while the lowest IWP in the dry year was 1.90 kg m−3. IWP was significantly higher in the rainy year, while WUE was significantly lower. On the other hand, WPet was more extensive in the wet year because the yield was higher, and the Evapotranspiration (ET) was smaller in comparison to the dry year.