Sufficient Water Supply Research Articles

The Challenge of Perioperative Fluid Management in Elderly Patients

The purpose of this chapter is to describe physiological changes occurring with age relevant to fluid therapy, and to discuss the influence of fluid therapy on outcome of surgery from this perspective. Dehydration, common among elderly people, is often mistaken for dementia or depression. Dehydration with dizziness increases the risk of falling, a predictor for adverse outcomes after surgery. Young volunteers can excrete up to 300 mmol sodium per liter urine. Elderly people cannot achieve such a concentration emphasizing the importance of giving water to excrete the osmoles given with intravenous crystalloids. Brain natriuretic peptide increases in cardiac disease and with age. Preoperative elevated levels predict adverse outcomes following surgery. The evidence and the physiology show that elderly patients benefit from a thorough regulation of fluid therapy keeping fluid balance close to zero (no more than 2 l positive) and with sufficient glucose and water supply.

Natural grasslands maintain soil water sustainability better than planted grasslands in arid areas

Planted grassland is one of the most quickly and effective way for vegetation restoration in arid and semi-arid regions. However, inappropriate grasslands construction can cause soil water deficit and soil drying in arid areas. In the present study, we evaluated the soil water storage deficit and soil water balance characteristics of different grassland types under natural conditions. The relative growth rates of planted grasslands, especially the planted legume grasslands, were approximately double higher than that of the natural grassland. Soil water storage deficit degree was the highest in the 0–50 cm soil layers than below the 50 cm layers. Soil water deficit degree was higher in legume grasslands than in gramineous grasslands below the depth of 50 cm, and it was significantly lower in the natural grassland than in planted grasslands below the depth of 200 cm (P < 0.05). The precipitation (P) was lower than the evapotranspiration (ET) in planted grasslands, thus resulting in soil water deficiency and soil desiccation. The average ET/P value was significantly higher in planted grasslands than in the natural grassland, and followed the order of planted gramineous grasslands> planted legume grassland and shrubland > natural grassland. None of the grasslands got sufficient water supply during the growing season for transpiration and growth. Our findings provided evidence that natural grasslands have lower water consumption, and indicated which vegetation types can maintain more soil water and facilitate vegetation sustainability when undertaking restoration in water-limited environments.

Challenges in water resources of Lagos mega city of Nigeria in the context of climate change

Abstract This study assesses the water resources and environmental challenges of Lagos mega city, Nigeria, in the context of climate change. Being a commercial hub, the Lagos population has grown rapidly causing an insurmountable water and environmental crisis. In this study, a combined field observation, sample analysis, and interviews were used to assess water challenges. Observed climate, general circulation model (GCM) projections and groundwater data were used to assess water challenges due to climate change. The study revealed that unavailability of sufficient water supply provision in Lagos has overwhelmingly compelled the population to depend on groundwater, which has eventually caused groundwater overdraft. Salt water intrusion and subsidence has occurred due to groundwater overexploitation. High concentrations of heavy metals were observed in wells around a landfill. Climate projections showed a decrease in rainfall of up to 140 mm and an increase in temperature of up to 8 °C. Groundwater storage is projected to decrease after the mid-century due to climate change. Sea level rise will continue until the end of the century. As the water and environmental challenges of Lagos are broad and the changing characteristics of the climate are expected to intensify these as projected, tackling these challenges requires a holistic approach from an integrated water resources management perspective.

Artificial Top Soil Drought Hardly Affects Water Use of Picea abies and Larix decidua Saplings at the Treeline in the Austrian Alps

This study quantified the effect of shallow soil water availability on sap flow density (Qs) of 4.9 ± 1.5 m tall Picea abies and Larix decidua saplings at treeline in the Central Tyrolean Alps, Austria. We installed a transparent roof construction around three P. abies and three L. decidua saplings to prevent precipitation from reaching the soil surface without notably influencing the above ground microclimate. Three additional saplings from each species served as controls in the absence of any manipulation. Roofing significantly reduced soil water availability at a 5–10 cm soil depth, while soil temperature was not affected. Sap flow density (using Granier-type thermal dissipation probes) and environmental parameters were monitored throughout three growing seasons. In both species investigated, three years of rain exclusion did not considerably reduce Qs. The lack of a significant Qs-soil water content correlation in P. abies and L. decidua saplings indicates sufficient water supply, suggesting that whole plant water loss of saplings at treeline primarily depends on evaporative demand. Future work should test whether the observed drought resistance of saplings at the treeline also holds for adult trees.

Predictors of water quality in rural healthcare facilities in 14 low- and middle-income countries

Abstract Many healthcare facilities (HCFs) in rural areas of low- and middle-income countries (LMICs) lack safe, sufficient water supplies. We sought to understand which factors affect water quality in rural HCF in LMICs. In Ethiopia, Ghana, Honduras, India, Kenya, Malawi, Mali, Mozambique, Niger, Rwanda, Tanzania, Uganda, Zambia, and Zimbabwe, doctors and nurses were interviewed at over 2000 outpatient HCFs about their water source, staff training, and management practices. Water samples were also tested for contamination with E. coli. We generated descriptive analyses and logistic regressions. Overall, 52% of surveyed HCFs used at least a basic water service, 23% used a limited water service, and 25% had no water service as defined by the WHO/UNICEF Joint Monitoring Programme. Use of an improved water source type (OR ≈ 1.4–1.7), treatment of water (OR = 1.26), management by a person with medical training (OR ≈ 3.4–8.9), and presence of a protocol for operations and management (OR = 1.29) were associated with safer water. These results suggest that in addition to addressing water source, storage, and treatment, stakeholders should also target organizational factors in order to improve water quality in HCFs.

Environmental analysis of soil characteristics in El-Fayoum Governorate using geomatics approach.

The present study aims at identifying the impact of wastewater irrigation on soil characteristics of El-Fayoum Governorate using Landsat images and geo-statistical techniques integrated with field investigation and soil analyses. Soil samples were collected from 40 representative sites during November/December 2016 and analyzed for pH, electric conductivity (EC), organic carbon (OC), total nitrogen (TN), total phosphorus (TP), Ca, K, Na, and Mg. Landsat images were processed to produce spectral indices of water (MNDWI), vegetation (NDVI), salinity (NDSI), and urban areas (NDBI). Inverse distance weighting in ArcGIS 10.1 was used for mapping soil characteristics. Results refereed to a fluctuation in soil characteristics among different districts, as a result of variation and severity of activities. High levels of OC (3.5-5.21%) were recorded in several scattered parts while northern parts showed high levels of TP and TN recording 0.8-1.7mg/g and 1.7-2.4mg/g respectively. A great fluctuation in salinity, Ca, K, and Na levels were detected among the collected soil samples. Southern and eastern borders of the governorate showed high levels of Ca (> 17.7mg/g). The most alkaline soil samples (> 8) were mostly recorded in El-Fayoum and Tamia districts. Variation of soil characteristics is greatly impacted by irrigation using wastewater particularly from El-Bats and El-Wadi drains. A strong positive correlation (0.94) was observed between urbanization (NDBI) and land salinization (NDSI) which ensures the negative impact of residential areas on agricultural lands. It can be concluded that the agricultural land problems have greatly been impacted by the lack of sufficient water supply. Geospatial techniques along with soil analyses facilitate studying such problems.

Comparing Macropore Exploration by Faba Bean, Wheat, Barley and Oilseed Rape Roots Using In Situ Endoscopy

Large-sized biopores in the subsoil can provide rapid access to deeper soil layers and potentially enhance nutrient acquisition. Besides site conditions, the extent of these effects depends on crop root architecture. The aim of this study was to compare barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), oilseed rape (Brassica napus L.) and faba bean (Vicia faba L.) with respect to time of macropore entry, root soil contact and root hair formation. Crops were grown in columns with condensed subsoil and an artificial macropore. Root growth dynamics in the macropore were monitored with in situ endoscopy. After harvest, the share of roots in macropores was quantified. Oilseed rape had many vertical roots with root hairs contacting the pore wall and was the only crop with preferential root growth in macropores. Cereal roots were mostly crossing the pore horizontally, partially with root hairs and partially contacting the pore wall. Nearly all faba bean roots were crossing the pore without root-soil contact. Our results support the notion that the importance of biopores for crop root growth and resource acquisition depends on root architecture. Under the conditions of the study with sufficient water supply and therefore comparatively low penetration resistance, macropores were only marginally used by cereals and faba bean. Oilseed rape roots were apparently much more sensitive to mechanical impedance, and the pores were used more intensively.

Anatomical and physiological adjustments of pubescent oak (Quercus pubescens Willd.) from two adjacent sub-Mediterranean ecosites

Patterns of drought severity in natural ecosystems depend on ecosite characteristics, particularly on local soil water availability and microclimate (evaporative demand). At the sites with less favourable conditions, the plasticity of fundamental drought adaptive traits can be exceeded under severe drought, even in well adapted species.In our study, anatomical and physiological adjustments to drought were studied in pubescent oak (Quercus pubescens Willd.) growing on adjacent sub-Mediterranean plots (ecosites) differing in bedrock and soil type (limestone with rendzic leptosol, low water retention - L; transition from limestone to flysch with eutric cambisol, high water retention - F).In both years of the study, 2015 and 2016, in the part of the season with sufficient water supply, sap flow density (SFD) was higher in oaks growing on L than those growing on F. With decreasing soil water content (SWC) in July, SFD was reduced on both plots, most in trees growing on limestone. In the period of severe drought, SFD in trees growing on L was decoupled from the changes of VPD, due to increased employment of water conservation strategies, such as decreases in stomatal conductance. This was further translated into stomatal limitation of photosynthesis and contributed to reduced radial stem growth.The seasonal dynamics of traits indicate that Q. pubescens trees use a predisposed anatomical strategy (average size of vessels in different years), adjusted to average ecosite conditions. At the same time, trees respond to local conditions and interanual variability of drought by shortening/prolonging the production and growth of vessels and by adjusting leaf functioning (stomatal conductance, sap flow) in accordance with hydraulic properties.

Repair of severe winter xylem embolism supports summer water transport and carbon gain in flagged crowns of the subalpine conifer Abies veitchii.

Xylem embolism induced by winter drought is a serious dysfunction in evergreen conifers growing at wind-exposed sites in the mountains. Some coniferous species can recover from winter embolism. The aim of this study was to determine whether wind direction influences embolism formation and/or repair dynamics on short windward and long leeward branches of asymmetrical `flagged' crowns. We analyzed the effect of branch orientation on percentage loss of xylem conductive area (PLC), leaf functional traits and the xylem:leaf area ratio for subalpine, wind-exposed flagged-crown Abies veitchii trees in the northern Yatsugatake Mountains of central Japan. In late winter, the shoot water potential was below -2.5MPa, and the PLC exceeded 80% in 2-year-old branches, independent of branch orientation within a flagged crown. Both of these parameters almost fully recovered by summer. At branch internodes 4years of age and older, seasonal changes in PLC were not found in either windward or leeward branches, but the PLC was higher in less leafy windward branches. The leaf nitrogen content and water-use efficiency of mature leaves were comparable between windward branches and leafy leeward branches. The ratio of xylem conductive area to total leaf area was the same for windward and leeward branches. These results indicate that the repair of winter xylem embolism allows leaf physiological functions to be maintained under sufficient leaf water supply, even on winter-wind-exposed branches. This permits substantial photosynthetic carbon gain during the following growing season on both windward and leeward branches. Thus, xylem recovery from winter embolism is a key trait for the survival of harsh winters and to support productivity on the individual level in flagged-crown A. veitchii trees.

Fraction of absorbed photosynthetically active radiation over summer maize canopy estimated by hyperspectral remote sensing under different drought conditions.

Fraction of absorbed photosynthetically active radiation (fAPAR) is one of the important remote sensing model parameters of vegetation productivity. However, the crop canopy fAPAR estimation during growing season under different drought conditions has not been reported yet. In this study, the characteristics of summer maize canopy fAPAR and spectral reflectance during growing season under different drought stresses and the relationships of fAPAR with reflectance, the first derivative spectral reflectance and vegetation indices were examined based on the hyperspectral reflectance and fAPAR data from the summer maize drought manipulation experiment with five irrigation levels in 2015. Under mild water stress and sufficient water supply conditions, fAPAR was higher, with the maximum value of 0.7. Under severe water stress and severe persistent drought, fAPAR was lower, with the minimum value of 0.06. Reflectance of visible and shortwave bands increased and near infrared reflectance decreased with increasing drought. The fAPAR was negatively related with visible bands and shortwave bands, but positively correlated with near infrared. Visible and shortwave band reflectance had significant correlation with fAPAR, especially at 383, 680 and 1980 nm, with all the correlation coefficients being more than -0.87. The strong and stable relationship between the first derivative spectral reflectance and fAPAR appeared at 580, 720 and 1546 nm, with the correlation coefficients being -0.91, 0.89 and 0.88, respectively. There were linear or logarithm relationships between fAPAR with nine vegetation indices. Among the nine indices, the enhanced vegetation index (EVI), renormalized difference vegetation index (RDVI), soil adjusted vegetation index (SAVI), and modified soil adjusted vegetation index (MSAVI) performed well with the correlation coefficient being higher than 0.88, and the average relative error (RMAE) 16.6%, 16.6%, 16.7% and 16.2%, respectively. Based on the logarithmic relationship between first derivative spectral reflectance and fAPAR, the simulation effect was best at the band of (720±5) nm, with a correlation coefficient of 0.86. The correlation coefficient of the relationship between fAPAR and reflectance was less than 0.81. The results could provide fAPAR simulation for remote sensing model of vegetation productivity and drought warning.

Assessing the impact of climate change on rainwater harvesting in the Oum Zessar watershed in Southeastern Tunisia

Climate change is believed to have a large impact on water resources system both globally and regionally. It has become a major global issue, especially in developing countries because these are most affected by its impacts. Rainwater harvesting techniques offer an alternative source of water and represent specific adaptive strategies to cope with water scarcity within future climate change. Studying the impact of climate change on rainwater harvesting techniques, however, is difficult, because the general circulation models (GCMs) which are widely used to simulate scenarios of future climate change operate on a coarse scale. We estimated the impact of climate change on water availability at the watershed level by downscaling precipitation and temperature from the GCMs using a statistical downscaling model. A water harvesting model then assessed the performance of the rainwater harvesting techniques for the Oum Zessar watershed in southeastern Tunisia under current climatic conditions and scenarios of future climate change. Annual temperature tended to increase and precipitation tended to decrease. These changes of climatic variables were used in the water harvesting model to simulate future water availability. Changing the directions of water flow between sub-catchments in combination with changing the spillway heights strongly affected the performance of rainwater harvesting under the scenarios of future climate, resulting in a sufficient water supply for 92% of all sub-catchments, compared to 72% without these changes.

Water crises in a water-rich country: case studies from rural watersheds of Nepal's mid-hills

Abstract The main objective of this paper is to assess the water crisis in Nepal by conducting a series of case studies in rural watersheds in the mid-hills. This was achieved through the applied qualitative method, especially combinations of desk study/structured searches, consultation, and field observation. The ground survey revealed that most of the rural communities in the mid-hills have an unreliable water supply. According to the local stakeholders, 20–25% of water resources have dried up as compared to 20 years ago. Drying up of water resources disproportionately affects women and girls in rural areas as women are responsible for household chores, including fetching drinking water. The findings also revealed that low-income households bear a disproportionate coping burden as compared to elite groups, as they often engage in coping strategies such as collecting water from distant water sources, which is labor- and time-intensive, and also yields smaller quantities of water. Assuming that unreliable water supplies will continue to exist in rural areas of the mid-hills for the foreseeable future, there is a critical need to consider which, if any, coping strategies will be most effective in ensuring that poor households will have access to safe and sufficient water supply.

Effects of free‐air CO2 enrichment and drought on root growth of field grown maize and sorghum

AbstractIncreasing CO2 concentration ([CO2]) is thought to induce climate change and thereby increase air temperatures and the risk of drought stress, the latter impairing crop growth. The objective of this study was to investigate the effects of elevated [CO2] and drought stress on root growth of one maize genotype (Zea mays cv. Simao) and two sorghum genotypes (Sorghum bicolor cv. Bulldozer and Sorghum bicolor × Sorghum sudanense cv. Inka) under the cool moderate climate of Central Europe. It was hypothesized that root growth stimulation due to elevated [CO2] compensates for a reduced root growth under drought stress. Therefore, we established an experiment within a free‐air carbon dioxide enrichment system (FACE) in 2010 and 2011. Sorghum and maize genotypes were grown under ambient [CO2] (385 ppm CO2) and elevated [CO2] (600 ppm CO2) and in combination with restricted and sufficient water supply. Elevated [CO2] decreased root length density (RLD) in the upper soil layers for all genotypes, but increased it in deeper layers. Higher [CO2] enhanced specific root length (SRL) of “Simao” and “Bulldozer,” however, did not affect that of “Inka.” “Simao” achieved a higher SRL than the sorghum genotypes, indicating an efficient investment in root dry matter. Although elevated [CO2] affected the root growth, no interaction with the water treatment and, consequently, no compensatory effect of elevated [CO2] could be identified.

Fire spread analysis for the 2017 Imizamo Yethu informal settlement conflagration in South Africa

On 11 March 2017, a large fire ravaged through the Imizamo Yethu informal settlement in Cape Town, South Africa, killing four people. A total of 2194 informal dwellings were destroyed, and over 9700 people were displaced. This paper presents an analysis of the spread of the fire and factors that contributed to the conflagration. This work is based on interviews with the firefighters that responded to the incident, the disaster management incident log of the day, photographic evidence from various sources, reports in the public domain and site visits. Over 170 firefighters drawn from across the City of Cape Town's Fire and Rescue Services battled for over 13.5 h to put out one of the largest fires to have happened in a South African settlement in recent times. The efforts by firefighters to tackle the fire were hampered by several factors among them, inaccessible or narrow driveways, the absence of sufficient water supply in the area, and certain community interactions. This work is novel as in the literature there is negligible data regarding fire spread analyses in informal settlements. This has hampered the development of evidence-based responses and fire safety interventions being developed, as it is sometimes unclear how to reduce fire spread. The rate of spread during the fire is approximately calculated. By understanding fire spread rates, community interactions and suppression challenges firefighting strategies, engineering designs and municipal responses to this problem can be enhanced.

Tomato yield and water use efficiency change with various soil moisture and potassium levels during different growth stages.

Faced with the scarcity of water resource and irrational fertilizer use, it is highly important to supply plants with water and fertilizer at desiderated stages to improve yield with high water use efficiency (WUE). A pot experiment was conducted to investigate the effects of growth stage-specific water deficiency and potassium (K) fertilization on tomato yield and WUE. The entire growing season of tomato was divided into 5 stages: vegetative growth stage (VG), flowering and fruit setting stage (FS), early fruit growth stage (FG), fruit development stage (FD) and fruit maturity stage (FM). Three soil moisture (W) and three K fertilization levels were set up. W levels included W1, W2 and W3, indicating that soil water was maintained at 60–70% field capacity, 70–80% field capacity, and 80–90% field capacity, respectively. K levels included K1, K2 and K3, indicating that 0 g K2O per kg soil, 0.46 g K2O per kg soil and 0.92 g K2O per kg soil was applied. All combinations of the three W and three K levels were solely imposed at each of the five growth stages, for other four stages, plants were watered to 80–90% field capacity without K fertilizer (W3K1). The permanent W3K1 over the entire growth stage was taken as control (CK). The results showed that W deficiency imposed at all stages significantly affected tomato yield (P<0.01), except for VG stage in which W deficiency did not cause yield loss. K fertilization level during FS or FM stage had a significant effect on yield (P<0.01). A significant interaction effect of W and K on yield was only observed during FM stage. For WUE, significant effect of W deficiency at FS, FD and FM stages were observed, and a significant effect of K levels at FS, FD and FM stages was observed. Specifically, K fertilization was necessary during specific growth stage of tomato (i.e. FS and FM). During FS stage, even if a sufficient water supply seems necessary, a deficit irrigation with K fertilization could be applied as K fertilization could alleviate the negative effect of soil water deficit, however, excess of K fertilization during FM stage should be avoided to maintain tomato yield and WUE.

Sink limitation of plant growth determines tree line in the arid Himalayas

Abstract Understanding what determines the high elevation limits of trees is crucial for predicting how tree lines may shift in response to climate change. Tree line formation is commonly explained by a low‐temperature restriction of meristematic activity (sink limitation) rather than carbon assimilation (source limitation). In arid mountains, however, trees face simultaneously low temperature and drought, both potentially restricting their growth and thus setting range limits. However, the mechanisms of tree line formation in high arid mountains are largely unknown. We studied Myricaria elegans, one of the world’s highest growing winter‐deciduous woody species, endemic to the arid Himalayas. We hypothesized that the upper elevation limit of Myricaria is associated with low temperatures during the early growing season affecting earlywood formation, while later in the season drought is constraining earlywood maturation and latewood formation. To test this hypothesis, we studied the quantitative anatomy of tree rings at different developmental stages across the entire species elevation range (3,200–4,400 m). We also explored daily stem increment and rehydration rates, seasonal dynamics of non‐structural carbohydrates and stable C isotopes as a proxy for possible drought constraints. Both earlywood and latewood increments decreased towards the tree line, while NSC in leaves, twigs and stem sapwood did not change, indicating a sink limitation as a main driver of the tree line. At tree line, low temperatures restricted earlywood formation more than latewood formation. Tree line individuals had—compared to individuals from lower elevations—smaller and fewer earlywood vessels, frequent frost rings and shorter periods with positive daily increments, but comparable night‐time stem rehydration rates and latewood density. All these results suggest a sink limitation as a main mechanism behind the tree line formation in high arid mountains. In the arid Himalayas, the tree line is set by the drastic growth reduction (sink limitation) caused by low temperature and short growing season under otherwise sufficient carbon and water supply. At the tree line, spring freezing and high summer temperatures further constrain annual stem increment. The mean 6.9°C temperature during the growing season places the Myricaria tree line within the thermal range of other high elevation tree lines worldwide and supports a common mechanism of alpine tree line formation. A plain language summary is available for this article.

Drought-tolerance mechanisms in foxtail millet (Setaria italica) and proso millet (Panicum miliaceum) under different nitrogen supply and sowing dates

Drought stress is one of the main limitations to crop growth and yield. Efficient nitrogen (N) nutrition may moderate the negative effects of drought stress on plants through retention of metabolic activities. The present study was conducted to investigate the biochemical responses of two millet species, foxtail millet (Setaria italica (L.) P.Beauv.) and proso millet (Panicum miliaceum L.), under two irrigation regimes (based on 55% and 85% soil-water depletion) and two N fertiliser levels (0 and 112.5 kg N ha–1) at four sowing dates (22 June and 6 July 2015, 14 and 30 June 2016). Drought stress increased hydrogen peroxide (H2O2), malondialdehyde (MDA) and other aldehyde contents of the plants, ultimately leading to 52% and 55% reductions in grain yield in foxtail millet and proso millet, respectively. Antioxidant activities showed significant increases under drought stress. Nitrogen application decreased H2O2, MDA and other aldehyde contents and activities of antioxidant enzymes, whereas it increased chlorophyll, carotenoid, phenolic compound and proline contents as well as grain yield. Higher grain yields were obtained with early planting dates under sufficient water supply, whereas superior yields were obtained with delayed planting dates under water stress owing to lower temperatures and evaporation rates. The results suggest that N application could mitigate the adverse effects of drought stress on millet plants by promoting osmoregulation, alleviating lipid peroxidation, and improving plant physiological traits. Foxtail millet had higher antioxidant potential than proso millet, resulting in greater capacity to inhibit production of free oxygen radicals and making it the more drought-tolerant species.

Water in the urban space of Dubrovnik

Many city wells and public cisterns, along with the water supply system built from the spring in Šumet to the urban centre in the fifteenth century, are an eloquent testimony of the great concern of the Dubrovnik authorities to provide its inhabitants with a sufficient and regular supply of fresh water. The mapping of public water locations inside the walled city area indicates the elite urban parts inhabited by the bulk of the nobility. Prior to the construction of the aqueduct, it was the area of Bunićeva poljana, today's Ulica od puča, in which the majority of wells had been dug. After the construction of the aqueduct, and in conformity with new communal solutions, the elite part shifted northwards, around the Placa, main street, which transformed into a new city centre

Poor-drainage-induced salinization of agricultural lands: Management through structural measures

Convenient and sufficient water supply to crops is a necessity for sustainable food production to the rising total populace. Albeit adequate water supply is important for crop production, the surplus water in the rootzone is hurtful to plant development and yield. Poor drainage and associated salinization represent severe threats to the long-term sustainability of irrigated agriculture in several dry areas. Reducing soil submergence, salinity control, and making new land accessible for agriculture are the three main goals of agricultural drainage. Thus, an effective drainage system not only improves the existing agricultural lands but also brings new areas under cultivation. This paper provides an investigation of different structural and engineering measures adopted for the management of drainage and salinization problems of irrigated lands. The overview of drainage and salinization problems and the requirement of a drainage system are presented. Application and limitations of surface drainage system in agricultural areas and the processes involved in the removal of surplus water through subsurface drainage system are provided. The adaptability and limitations of tile drainage, mole drainage, and vertical drainage in managing the drainage and salinization problems of agricultural lands are also detailed in the paper. Finally, policy issues are discussed and some conclusions are provided.

Investigation of Post-Fire Debris Flows in Montecito

Debris flows in a burned area, post-fire debris flows, are considered as one of the most dangerous geo-hazards due to their high velocity, long run-out distance, and huge destruction to infrastructures. The rainfall threshold to trigger such hazards is often reduced compared with normal debris flow because ashes generated by mountain fires reduce the permeability of the top soil layer, thus increasing surface runoff. At the same time, burnt material and residual debris have very poor geo-mechanical characteristics, e.g., their internal friction angle and cohesion are typically low, and thus an intense rainfall can easily trigger some debris flows. Studying post-fire debris flow enables us to get a deeper understanding of disaster management. In this paper, the debris flow that occurred in Montecito, California, USA, and was affected by the Thomas Fire was used as a case study. Five major watersheds were extracted based on the digital elevation model (DEM). Remote sensing images were used to analyze the wildfire process, the extent of the burned areas, and the burn severity. The hypsometric integral (HI) and short-duration rainfall records of the watersheds around Montecito when the post-fire debris flows occurred were analyzed. Steep terrain, loose and abundant deposits, and sufficient water supply are the important conditions affecting the formation of debris flows. Taking watersheds as the research objects, HI was used to describe the geomorphic and topographic features, open-access rainfall data was used to represent the water supply, and burn severity represented the abundance of material sources. An occurrence probability model of post-fire debris flow based on HI, short-duration heavy rainfall, and burn severity was developed by using a logistic regression model in post-fire areas. By using this model, the occurrence probability of the post-fire debris flow in different watersheds around Montecito was analyzed based on the precipitation with time. Especially, the change characteristics of occurrence probability of debris flows over time based on the model bring a new perspective to observe the obvious change of the danger of post-fire debris flows and it is very useful for early warning of post-fire debris flows.