Rainfall Deficit Research Articles

Rainfall Variability and Rice Production: An Assessment Based on the Variability in Indian Monsoon and Ground Water Level of Punjab, India

In Punjab, 99 per cent of total cultivated area is under irrigation but it is at the cost of declining ground water table. Due to rainfall variability and very high requirement of water in rice crop, which occupy large area in the state during kharif season, has further deteriorated the situation of water resources. Therefore, this study was conducted to identify the relationship between declining groundwater level, variable monsoonal rainfall and rice yield of different agroclimatic zones of Punjab. The historical data of rainfall for different locations of Punjab viz. Amritsar (1998-2017), Ballowal Saunkhri (1998-2017), Bathinda (1998-2017), Ludhiana (1998-2017) and Patiala (1998-2017) was collected from the Department of Climate Change and Agricultural Meteorology, PAU, Ludhiana and Met Centre, IMD Chandigarh. The productivity data of rice was collected from indiastat.com and Statistical Abstract of Punjab whereas the data related to groundwater table (1998-2017) were collected from the Central Ground Water Board, Punjab. It was observed that the ground water table level showed significant decrease after 2005 at all locations and there was a positive correlation between rice yield and ground water table at all the locations except at Amritsar where it was negatively correlated. The deficit rainfall years showed very less impact on rice yield which has increased continuously. However, the relationship between groundwater table and rainfall indicated that deficit monsoonal rainfall led to further decline in groundwater table as it was not recharged.

Heat and Moisture Anomalies During Crop Failure Events in the Southeastern Australian Wheat Belt

AbstractProlonged droughts and heatwaves are common causes of agricultural failure in Australia, yet the origins of these climate anomalies remain understudied. Here, we use a Lagrangian trajectory model driven by atmospheric reanalysis and constrained by satellite data to unravel the sources of precipitation and heat over the Southeastern Australia wheat belt. Furthermore, we assess the impact of local and upwind drought conditions on the moisture and heat imports to the region. Results indicate that the most extreme crop failure events over the wheat belt (i.e., 1994, 2002, and 2006) were associated with persistent high‐pressure systems. The ocean provided on average 72% of the moisture for precipitation and 39% of the heat arriving over the wheat belt, with the moisture sources substantially decreasing during crop failure events. Upwind drought further intensified rainfall deficits and heat stress during these events due to lower moisture and higher heat imports to the region. This was particularly clear during the initial phase of the Millennium Drought in 2002. Then, yield deficits exceeded 50%, and ∼4% of the precipitation originated from drought‐affected regions upwind, compared to the 9% that was expected climatologically from those regions. Simultaneously, the heat import from these regions upwind increased by ∼10 W m−2, from the climatological 23%–25%, during this event. While these results indicate a limited potential for upwind land management to mitigate downwind agricultural loss in the Southeastern Australia wheat belt, other agricultural regions with a higher climatic dependency on remote land may benefit from such strategies.

Rainfall trends and spatiotemporal patterns of meteorological drought in Menna watershed, northwestern Ethiopia

Understanding the spatiotemporal patterns of drought is crucial for planning, disaster preparedness, vulnerability assessment, impact evaluation, and policy formulation to mitigate drought-induced effects. The purpose of this study was to assess rainfall trends and spatiotemporal patterns of meteorological drought using geospatial techniques in Menna watershed. The Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) rainfall, and station-based observed rainfall were the datasets used. The station-based rainfall was used to confirm the accuracy of CHIRPS rainfall data. The Mann-Kendall (MK) test and Sen's slope estimator were utilized to assess trends and ascertain the extent of change. To characterize meteorological droughts, percent of normal (PN), standardized anomaly index (SAI), and standardized precipitation index (SPI) were computed during the crop growing seasons (2000–2022). The validation result confirmed a strong agreement between the observed and CHIRPS rainfall data (R2 = 0.88). Based on the MK test, an increasing trend has been observed in annual (3.7 mm/year) and belg (3.4 mm/year) rainfall, which was significant at p < 0.05. But the kiremt season was slightly decreasing (−0.7 mm/year). The PN, SAI, and SPI values detected that 2002, 2004, 2009, 2011, 2014, 2015, and 2019 were drought years in the area. Even only 1.4, 0.2, and 0.5% of the watershed were free from drought in 2009, 2014, and 2015, respectively, due to extremely high rainfall deficiency. Conversely, 2001, 2010, and 2016 were notable for having the highest amounts of rainfall compared to the other years. Generally, the region could be classified as an area highly susceptible to meteorological drought in northwestern Ethiopia. There was no even a single year free from drought in the entire study period. To that extent, about 86% of it had repeatedly encountered extreme rainfall deficit (7–23 times) during the study period. Thus, the population has always been repeatedly smashed down by the frequent droughts. To tackle existing challenges and mitigate upcoming risks, continual droughts monitoring and implementation of efficient early warning systems are vital for the region.

Temporal Variability of Rainfall and Trend Analysis of Melloulou Watershed in Morocco

This paper focuses on analyzing the temporal variability of rainfall and rainfall trends using a statistical analysis of rainfall data in the Melloulou watershed for a half-century chronicle (1970-2020). The objective of this study is to extract all the rainfall characteristics and the rainfall variability during this period to determine the rainfall trends. The working method is based on a statistical approach to detect the climatic characteristics of the Melloulou basin. The study of the standardized precipitation index (SPI) and the rainfall deficit index (RDI) showed the alternation of very long dry periods with wet periods. The Mann-Kendall test under the RStudio also showed a decreasing rainfall trend.

Unusual subseasonal variability of Indian summer monsoon rainfall in 2020

AbstractAbove‐normal all‐India summer monsoon (ISM) rainfall was received in 2020 with 109% of its long‐period average. According to the India Meteorological Department (IMD), ISM 2020 experienced robust month‐to‐month rainfall variations; in particular, the peak monsoon month of July 2020 witnessed deficit rainfall. The present study investigated the possible mechanisms that are responsible for the July 2020 deficit rainfall. Analysis revealed that the strong low‐level moisture divergence caused by the westward‐propagating atmospheric Rossby wave, induced by suppressed western North Pacific (WNP) convection, is primarily responsible for the July rainfall deficit. The WNP suppressed convection is linked to anomalous low‐level anticyclonic circulation. It is noted that the intense WNP anticyclone is maintained by the tropical Indian Ocean (TIO) warming‐induced atmospheric Kelvin waves and strong low‐level convergence over the Meiyu‐Baiu rainband. Unlike July, the strength of the WNP anticyclone and TIO warming are weaker in June and August. In addition to the observational analysis, the skill of the Climate Forecast System version‐2 (CFSv2) model in predicting the July rainfall at a lead of about two months is examined. Strong positive rainfall anomalies over India are predicted by the model in July, which is in contrast to the observations. Despite predicting the TIO warming, the model failed to capture the westward extension of the WNP anticyclone, which impacted the July rainfall prediction. To understand the importance of the WNP anticyclone on ISM rainfall, a CFSv2 sensitivity experiment is carried out by imposing strong negative sea surface temperature (SST) anomalies over the WNP region to excite the anticyclone. Both the westward extension of the WNP anticyclone and suppressed rainfall over the core monsoon region in July are captured by the model when low‐level circulation is imposed. The model sensitivity experiment strongly supports the role of the WNP anticyclone and its westward extension in inducing reduced rainfall in July 2020 over the monsoon trough region.

Extreme drought triggers parallel shifts in wood anatomical and physiological traits in upper treeline of the Mediterranean Andes

BackgroundTreeline ecotones of Mediterranean ecoregions have been affected by the increasing intensity and severity of droughts. Even though the effect of droughts on forest dynamics has been widely documented, knowledge is relatively scarce of how extreme climate episodes affect the hydraulic structure and, therefore, the physiology of woody plants. The Mediterranean Andes have experienced an uninterrupted period of drought since 2010, including an extremely dry year in 2019 with approximately 80% rainfall deficit. Here, we investigated shifts in wood anatomical and physiological traits of Kageneckia angustifolia, an endemic treeline species, in response to this drought period.MethodsWe evaluated the xylem plasticity of three K. angustifolia populations across their natural distribution (31–35° SL) based on anatomical (vessel structure and distribution) and physiological (intrinsic water-use efficiency) variables in the tree rings. We focused on the period 2000–2020 that corresponds to before the megadrought (2000–2007), (ii) megadrought (2008–2018) and (iii) hyperdrought (2019–2020). The variables were annualized and analyzed by linear mixed-effects models.ResultsOur results provide insights to the anatomical and physiological mechanisms underlying the resilience of treeline forests to persistent droughts in central Chile. We found that the extreme drought in 2019–2020 triggered shifts in vessel size and frequency that increased hydraulic safety. These significant shifts in vessel traits occurred in parallel with a decrease in pit aperture area and an increase in water-use efficiency, further increasing the resilience of K. angustifolia to extreme drought stress.ConclusionsOur results revealed coordinated shifts in vessel size and frequency and water-use efficiency in response to the megadrought, thereby reducing vulnerability to hydraulic failure. The apparent resilience of K. angustifolia to extreme droughts suggests that this adaptation to drought stress may increase its ability to tolerate novel climatic conditions of treeline environments of the Mediterranean Andes, although it is not clear whether these adaptations will be sufficient to persist in scenarios that predict intensification of climate stress. Finally, our results provide empirical evidence that integrating wood anatomical and physiological traits facilitates the understanding of resilience mechanisms that treeline forests develop in the face of increasing drought stress.

Divergent future drought projections in UK river flows and groundwater levels

Abstract. Hydrological drought is a serious issue globally, which is likely to be amplified by 21st century climate change. In the UK, the impacts of changes in river flow and groundwater drought severity in a future of climate change and higher water demand are potentially severe. Recent publication of a new nationally consistent set of river flow and groundwater level projections (the eFLaG dataset), based on state-of-the-art UKCP18 climate projections, offers a unique opportunity to quantitatively assess future UK hydrological drought susceptibility. The dataset includes a transient, multi-model ensemble of hydrological projections driven by a single regional climate model (RCM), with a 12-member perturbed-parameter ensemble, for 200 catchments and 54 boreholes spanning a period from 1961 to 2080. Assessment of a baseline period (1989–2018) shows that the RCM-driven projections adequately reproduce observed river flow and groundwater level regimes, improving our confidence in using these models for assessment of future drought. Across all hydrological models and most catchments, future low river flows are projected to decline consistently out to 2080. Drought durations, intensities and severities are all projected to increase in most (over 90 %, pooling across different drought characteristics) UK catchments. However, the trajectory of low groundwater levels and groundwater drought characteristics diverges from that of river flows. Whilst groundwater levels at most (&gt; 85 %) boreholes are projected to decline (consistent with river flows), these declines are relatively modest (&lt; 10 % reduction) in transient low groundwater levels by 2080, and, in fact, six show moderate increases. Groundwater drought characteristics in the far future (2050–2079) are often similar to those of the baseline (1989–2018), with only 33 % of boreholes showing an increase (towards worsening drought) of more than 10 % for drought severity (48 % of boreholes for drought intensity). Interestingly, for some boreholes, droughts are projected to be more prolonged and severe in the near future (2020–2049) before returning to shorter durations and lower severity in the far future. A number of explanatory factors for this divergence between river flow and groundwater are discussed. The sensitivity to seasonal changes in precipitation and potential evapotranspiration is proposed as a principal driver of divergence because low river flows are more influenced by shorter-term rainfall deficits in the summer half-year, whilst groundwater drought appears to be offset somewhat by the wetter winter signal in the RCM projections. Our results have important implications for water management, demonstrating a widespread increase in river flow drought severity and diminishing low flows that could have profound societal and environmental impacts unless mitigated. Furthermore, the divergence in projections of drought in river flows and groundwater levels brings into question the balance between surface and subsurface water resources. The projected contrast in fortunes of surface and subsurface water resources identified for the UK may be replicated in other parts of the world where climate projections suggest a shift towards drier summers and wetter winters.

Temporal Variability of Rainfall Amounts and Trend Analysis in the Melloulou Watershed

The present study consists in analyzing the temporal variability of rainfall and rainfall trend a statistical analysis of rainfall data in the Melloulou watershed for a half-century chronicle (1970-2020). The objective of this study is to extract all the rainfall characteristics of this period, to extract the rainfall variability and to determine the rainfall trends. The working method is based on a statistical approach to detect the climatic characteristics of the Melloulou basin. The study of the standardized precipitation index (SPI) and the rainfall deficit index (IDF) showed the alternation of very long dry periods with wet periods. The Mann-Kendall test under the RStudio also showed a decreasing rainfall trend.

Sustainable Water Management of Drip-Irrigated Asparagus under Conditions of Central Poland: Evapotranspiration, Water Needs and Rainfall Deficits

Water is a valuable yet scarce resource in agriculture. Optimizing crop production relies on irrigation, but within the framework of sustainable agriculture, efforts should prioritize reducing irrigation water usage. Unfortunately, climate change increases plant water requirements, consequently heightening the need for irrigation. The aim of the research was to estimate the water needs of asparagus during the fern growth period (21 June–31 August) using the Blaney–Criddle method. The study also aimed to determine trends in changing water needs and estimate precipitation deficits. Calculations were carried out for the years 1981–2020 across four provinces in central Poland. The research indicated that water needs varied between 233 mm and 242 mm, depending on the province. Over the forty-year period, all provinces displayed an increasing trend in water needs, with a rise of 3.1 mm to 6.2 mm per decade. Between 21 June and 31 August, rainfall deficits occurred with varying intensity in all provinces during normal, medium dry and very dry years. The values of water needs and rainfall deficit, calculated as a result of the research, are of key importance in the design, construction, and management of drip irrigation systems for asparagus plantations in central Poland.

Unveiling the climate–conflict nexus: Examining the influence of weather extremes on conflict emergence in the Philippine Bangsamoro

Extreme weather events have been closely associated with the escalation of violent conflicts. This article introduces empirical evidence that underscores the vulnerability of conflict emergence to extended deficit rainfall values within Maguindanao, a province situated in the Bangsamoro region of the southern Philippines. Using a combination of satellite data, hydrological analysis and an examination of conflict databases, our study unveils the pivotal role played by protracted droughts and intensified precipitation in fostering human insecurity, consequently elevating the likelihood of violent conflicts. Our research spotlights the climate–conflict nexus within this relatively less-explored geographical area. Our findings underscore a robust association between instances of violent conflicts, protracted deficits or episodes of intense rainfall, and the subsequent surge in food prices. Notably, disruptions in food prices align temporally with heightened participation in violent conflicts by individuals. In essence, the emergence of violent conflicts exacerbates fragility, thereby engendering a vicious cycle that intertwines climate change, conflict dynamics and the pursuit of peace.

Viability of Distributed Generation with Biogas and Photovoltaic in an Isolated System

In the 1970s, the Brazilian oil crisis sparked interest in researching inexhaustible sources of energy. Within these sources of energy, those known as clean and abundant have become a viable alternative, reducing the pollutant capacity of waste, because the gas emitted by them in the decomposition that would previously go to the environment, is now destined for energy production and solid portion used as organic fertilizer [5]. This work aims to implement a case study to estimate the economic viability of the project, hybrid sources, in rural areas. The project in question will be analysed through software and mathematical methods, guaranteeing results close to those calculated analytically, compared to the energy sources studied as well as their feasibility and profitability through isolated distributed generation, which can bring fast and safe returns, such as a return of 84.37% biogas and 77.76% for photovoltaic compared to the initial investment over 25 years. Currently, Brazil suffers from a shortage of rainfall and consequently, with problems in the energy matrix, since the majority of Brazilian electricity comes from a hydroelectric power plant. Therefore, the purpose of this study is to present a solution and consequently self-sufficiency in rural areas, taking advantage of biodigesters and abundant sun to produce electricity.

Skin microbiome disturbance linked to drought-associated amphibian disease.

The onset of global climate change has led to abnormal rainfall patterns, disrupting associations between wildlife and their symbiotic microorganisms. We monitored a population of pumpkin toadlets and their skin bacteria in the Brazilian Atlantic Forest during a drought. Given the recognized ability of some amphibian skin bacteria to inhibit the widespread fungal pathogen Batrachochytrium dendrobatidis (Bd), we investigated links between skin microbiome health, susceptibility to Bdand host mortality during a die-off event. We found that rainfall deficit was an indirect predictor of Bd loads through microbiome disruption, while its direct effect on Bd was weak. The microbiome was characterized by fewer putative Bd-inhibitory bacteria following the drought, which pointsto a one-month lagged effect of drought on the microbiome that may have increased toadlet susceptibility to Bd. Our study underscores the capacity of rainfall variability to disturb complex host-microbiome interactions and alter wildlife disease dynamics.

Drought Analysis in Right Bank Main Canal Command Area of Dharoi Reservoir using Meteorological and Remote Sensing Indices

Drought is characterized by a prolonged and abnormal lack of moisture, often stemming from insufficient or uneven distribution of precipitation, resulting in water shortages in streams or reservoirs, with detrimental impacts on both natural and socioeconomic systems. The paper focuses on the climatic drought patterns within the Right Bank Main Canal Command Area of Gujarat’s Dharoi Reservoir. To evaluate drought conditions, the study employs several indices including the Standardized Precipitation Index (SPI)and Normalized Difference Vegetation Index (NDVI). Daily rainfall data, obtained from IMD gridded data and extracted using ArcGIS software, is utilized to calculate SPI values at a three-month time scale. NDVI is determined using Landsat-8 OLI data spanning from 2013 to 2022 to analyze changes in agricultural vegetation. Comparisons among NDVI and SPI reveal that the year 2018 experienced significant rainfall deficits across the region, leading to severe water scarcity. This shortage impacted agricultural practices, evident in reduced crop cultivation areas as indicated by NDVI results and validated using the crop yield data for the time series. Specifically, the NDVI analysis highlights that 33.5% of the RBMC command area exhibited signs of dryness, with an additional 64.5% showing moderate dryness. The study endeavors to pinpoint drought-affected regions utilizing precipitation data, reservoir storage information, and remote sensing methodologies.

The combined influence of west Pacific subtropical high and tropical cyclones over the northwest Pacific on Indian summer monsoon rainfall

AbstractWe examined the interrelationship between the Indian summer monsoon rainfall (ISMR), the west Pacific subtropical high (WPSH), and tropical cyclone (TC) activity over the western north Pacific (WNP) Ocean during the peak monsoon season in 1951–2019. When WNP TCs are inactive (active), there is a noticeable 10° westward (eastward) shift observed along with intensification (weakening) of the WPSH. The WPSH and WNP TC activities are divided into four categories—an eastward shift of WPSH with active TCs (EA) and inactive TCs (EI), and a westward shift of WPSH with active TCs (WA) and inactive TCs (WI)—in order to investigate the combined influence of the WPSH and WNP TCs on ISMR during non‐El Niño–Southern Oscillation (non‐ENSO), El Niño, and La Niña phases. In the EA non‐ENSO cases, a surplus (deficit) rainfall was noticed over central (southern peninsular) India as a result of moisture convergence (low convective available potential energy, abnormal moisture divergence and downdraft); however, the rainfall is above normal over the Indian subcontinent. During the EI non‐ENSO case, an excess (deficit) regional rainfall activity was observed over east‐central India and parts of north India (southern peninsular India) through regional changes in atmospheric circulations and midtropospheric vertical velocity. In contrast, in WI (WA) non‐ENSO cases, the majority of India (southern peninsular and northeast India) experiences excessive precipitation while east‐central India (east and west central India) undergoes a deficit rainfall. This pattern is consistent with the spatial distribution of moisture flux convergence, convective available potential energy, and midtropospheric vertical velocity. In the case of non‐ENSO, the westward shift of the WPSH associated with inactive TCs is one of the favourable conditions for ISMR. In general, the effect of an eastward (westward) shift of the WPSH along with more (less) TCs during the non‐ENSO case is favourable to ISMR. On the other hand, rainfall patterns during ENSO are significantly associated with the circulation changes teleconnected to El Niño and La Niña conditions.

Identifying important drivers of East African October to December rainfall season

Monsoon rainfall plays a crucial part in Africa's socio-economic structure and its year-to-year variability has profound implications for agricultural, energy, and other societal sectors. The current study focuses on two of the major climate drivers of the east African rainy season during October-November-December (OND), which is when the season starts for a large portion of east Africa (e.g. Tanzania and Malawi). Such drivers could be different in early austral summer from the rest of the year, due to the relative positioning of the Intertropical convergence zone, which passes through this region - hence regions of east Africa and OND season are the focus here.The two drivers of Monsoon viz. El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are considered: both independently indicate strong connections with monsoon OND rain. Not only is there a strong significant positive correlation in the OND season as a simultaneous relation, but the signal is also there even with the lag of a few months. This has been tested using various data sources, detrending data beforehand, analysing either recent time periods or earlier time periods - covering two decades each, and using regression analyses. To further strengthen the results, a compositing approach is applied that can additionally identify strong rainfall signals to that from years when opposite combinations of ENSO and IOD phases act as confounding factors.Results of precipitation anomaly for OND for compositing, when IOD and ENSO are both negative (positive) in July–August-September(JAS) indicate a deficit (excess) in rainfall in that region. The Walker circulation seems to play a major part via altering ascending to descending branch in two situations, when both drivers are in same phase. In the last near thirty years period, a total of 9 years matched the criteria when both drivers were negative and suggested a deficit in OND rainfall; more recently, that criteria occurred also in 2022 (JAS) and was again associated with a rainfall deficit in OND 2022. Based on this analysis, it is possible to deliver an estimation of cumulative rain in terms of median value, range and distribution, one season in advance, at a point location or average over a region.Some results of compositing are confirmed for longer record (1940–2021) too and further classifications based on threshold of drivers are tested. Rainfall (OND) variability at intra-decadal, decadal and multi-decadal scales are studied by applying the method of centered moving averages of 5-year, 11-year and 21-year respectively. Our results have implications for future planning in optimizing agricultural and energy outputs, mitigating severe consequences and losses associated with droughts and excess rain and will impact the livelihoods of millions of east Africans.

ASSESSMENT OF IRRIGATION WATER REQUIREMENTS FOR APPLES, PEARS, AND PLUMS IN THE KOLUBARA AND MORAVA DISTRICTS UNDER CHANGING CLIMATE CONDITIONS

Climate change, which manifests through shifts in temperature, rainfall patterns, and the frequency of extreme events like droughts and floods, has a substantial impact on agricultural production and food security. This study investigates the influence of climate change on the irrigation needs of apple, pear, and plum crops in two fruit-growing districts in western Serbia, specifically in the Kolubara and Morava districts. This research aims to provide valuable insights for farmers to plan and adapt their production strategies in response to evolving climate conditions. To estimate the water requirements, crop evapotranspiration (ETc), effective rainfall (Pe), and water deficit (In) were determined using historical climate data from meteorological stations in Valjevo (Kolubara district) and Požega (Morava district) for the observed period (1961 - 2021). For projecting future water requirements (2021 - 2040), we employed data from eight regional climate models within the EURO – CORDEX project. The analysis of water requirements for apple, pear, and plum was conducted for both grassed and non-grassed orchards.&#x0D; In the Kolubara district, the average seasonal water deficit during the observed period was 356 mm in grassed orchards and 191 mm in non-grassed orchards, with the most significant irrigation requirements occurring in July and August, representing 60 - 70% of the seasonal water requirement. Looking ahead to the future period (2021 - 2040), the average water deficit increases to 401 mm in grassed orchards and 202 mm in non-grassed orchards, marking a 13% and 6% rise, respectively, compared to the observed period. This signifies a need for 1 to 2 additional irrigation sessions. In the Morava district, the average seasonal water deficit during the observed period was 403 mm in grassed orchards and 236 mm in non-grassed orchards, with the highest irrigation requirements in June, July, and August, accounting for 80 - 90% of the seasonal water requirement. Due to an anticipated increase in total precipitation in the future period (2021 - 2040) in the Morava district, there is a decrease in the seasonal water deficit by 3% in grassed orchards and 16% in non-grassed orchards. However, even with reduced water requirements in the future, there remains a significant requirement for irrigation in May, June, July, and August when rainfall is limited.

Development of low-cost rainwater harvesting to support on-site water supply in rural Tajikistan

Farmers in remote, arid areas, far from available water sources, need affordable water solutions for household and livestock use. In this study, the water needs and potential for rainwater harvesting (RWH) in the Kysylsu River Basin are estimated at different altitudes. The mean annual net rainfall depth varied from 545 to 900 mm. With an average roof area of 550 m2, 211 m3 to 344 m3 rainwater can be harvested for dry and wet years respectively. Based on the estimated water demand and rainfall deficit, the average household need was estimated to be 100 m3. For a low-cost water storage solution, we tested different types of waterproof materials to replace smaller 12-18 m3 concrete tanks commonly used in the region. Soil pits lined with 0.3 mm double layer polyethene (0.6 mm in total) was the best solution for 5 m3 volume tanks in terms of the costs and durability and 0.8 mm double layer polyethene (1.6 mm in total) was ideal for sealing 10 m3 volume tanks. This study demonstrates the efficiency of the system for improved livelihood of the families through rain harvesting.

Characterization of the Hydrological Balance and Assessment of the Recharge of Fractured Aquifers in the Context of Climatic Variability in Siguiri

Climate change in the Siguiri prefecture is having a considerable impact on the water balance. With the aim of determining the hydrological balance and the quantity infiltrated into the aquifers, groundwater resources can be assessed. To carry out the study, we focused our analyses on climatic parameters (rainfall, temperature), which led to the determination of groundwater recharge in the aquifers. We found an average temperature of 26°C, with a maximum temperature of 39°C in April. The minimum temperature from December to January was 13°C. Rainfall during the dry season (November, December, January, February, March and April) was 54 mm. The average rainfall during the wet season (May, June, July, August, September, October) is 1142 mm. The imbalance in the water balance is explained by the amount of water infiltrated (41 mm or 3% of rainfall). This value, which represents a volume of 717.5 million m3 per year, is deemed sufficient to meet the needs of the population of Siguiri (695,449 inhabitants with a growth rate of 3%). Groundwater resources have been affected by rainfall deficits and variability in groundwater levels over the last forty (40) years (1980-2020) in the various localities in the study area. Precipitation water runs off (90%) more than it infiltrates (3%) into the aquifer horizons of the Siguiri prefecture, making access to drinking water difficult during the dry season for the population of Siguiri.

Interplay between climate change and climate variability: the 2022 drought in Central South America

Since 2019, Central South America (CSA) has been reeling under drought conditions, with the last 4 months of 2022 receiving only 44% of the average total precipitation. Simultaneously to the drought, a series of record-breaking heat waves has affected the region. The rainfall deficit during October–November-December (OND) is highly correlated with the Niño3.4 index, indicating that the OND 2022 rainfall deficit is partly driven by La Niña, as observed in previous droughts in this region. To identify whether human-induced climate change was also a driver of the OND 2022 rainfall deficit, we analysed precipitation over the most impacted region. Our findings revealed a pattern of decreased rainfall over the past 40 years, although we cannot definitively conclude whether this trend exceeds what would be expected from natural variations. To clarify if this trend can be attributed to climate change, we looked at 1-in-20-year low rainfall events over the same region in climate models. The models show that the severity of low rainfall events decreases (i.e. they become wetter, the opposite of the trend observed in most weather records), although this trend is again not significant and is compatible with natural variability. Therefore, we cannot attribute the low rainfall to climate change. Moreover, our analysis of effective precipitation potential (evapotranspiration minus rainfall) shows that, in climate models, the increase in temperature does partly compensate for the increase in rainfall but only to offset the wetting, and does not lead to a significant climate change signal in effective precipitation. However, higher temperatures in the region, which have been attributed to climate change, decreased water availability in the models in late 2022, indicating that climate change probably reduced water availability over this period also in the observations, increasing agricultural drought, although this study did not quantify this effect. This means that even though the reduced rainfall is within the natural variability, the consequences of drought are becoming more severe due to the strong increase in extreme heat. The case of the OND 2022 rainfall deficit and the ongoing drought in CSA is a clear example of the interplay between climate variability and human-induced climate change. This shows the importance of considering not only those aspects associated with climate change but also climate variability in order to understand and attribute particular events or trends at the regional level.

Hop cultivation vs. weather – an eternal theme

The course of weather conditions during the growing season, but also beyond it, decides the economics of hop cultivation every year. Ongoing climate changes manifested by more frequent occurrence of compound hot and dry waves affect hop cultivation not only in the Czech Republic, but in the entire region of Central Europe. The paper evaluates the harvest results (yields, alpha acid content) of four Czech hop varieties in the period 2019–2022 with a focus on the weather diametrically opposed vintages 2021 and 2022 on a specific agricultural farm in the Žatec (Saaz) hop-growing region. While the 2021 vintage was rich in precipitation in the decisive vegetation phase, the 2022 vintage was very dry and hot. The age of the plants significantly influenced the alpha acid content of the varieties Saaz, Sládek and Premiant independently of the vintage. Young growths of the Saaz variety contained at least 60% rel. more alpha acids than older growths (more than 5 years old), while the increase in the Sládek variety was 30–40% rel. and in the Premiant variety 20–25% rel. In the case of the variety Agnus, the age of the plants did not have a demonstrable effect on the content of alpha acids. In 2021 the yields of all varieties were negatively affected by the calamitous occurrence of downy mildew. In 2022, the rainfall deficit was so large that it could not be fully compensated even by the maximum use of drip irrigation. Of the evaluated varieties, the Agnus variety coped best with the different weather conditions of the assessed vintages. This shows that the cultivation of climate resistant varieties is one of the promising but time-consuming ways to face the expected climate changes. Other options include regular renewal of hop growths, consistent regionalization, i.e. planting hop in locations that are suitable for the given variety and efficient use of irrigation systems.