水文学: 現在の研究

This study has analyzed the climate variability and meteorological drought events over Limpopo River Basin. The Limpopo Basin is shared by four countries, Botswana, South Africa, Zimbabwe, and Mozambique. The total catchment is approximately 408,000 km2. The main governing factor for rainfall patterns in the basin is the movement of the Inter-tropical Convergence Zone (ITCZ). In this study the drought event has been analyzed using standardized precipitation index (SPI). The SPI quantifies the precipitation deficit for multiple time scales and reflects the impact of droughts on the availability of water resources. The long year`s daily average monthly precipitation for the whole area indicates that the precipitation is variable and there is no any clear trend. The relative percentage change of average monthly precipitation of the 1992-2001 compared to 1961-1991 period using WATCH Climate data of the River basin indicates that, a positive value increase in percentage change is observed for the whole months of the year. High magnitude deviation in maximum and minimum temperature in the month of July 2001 observed with respect to 1961-2000 period. 5.2 and 7.9 degree centigrade respectively. The long term SPI analysis indicates that there was an extended accumulated sever dry condition that is prolonged from 1991 up to 1992 over the basin. Generally, this study indicates that there is a frequent meteorological drought events and unpredictable climate variability in the basin. Therefore farmers should take a precaution to adjust their farming system and to overcome drought events for better agricultural productivity.

Knowledge about variability of temperature, precipitation, snowpack and snowmelt with temperature and elevation are essential to prepare input data for hydrological models. The study presents characteristics and variability of these input variables during springtime at three elevations (Bhang, Solang and Dhundi stations in the Solang Valley of the western Himalaya) with respect to mean temperature (Tm) at Bhang using weekly data within a period of 27 years with initial (1982 and 1983) and later (2008 and 2009) consecutive years including decadal years 1993 and 2003. Methodology comprises of process integration using regression, simulation, cluster analysis, transformation, projection and inter-annual comparison. Study shows that temperature lapse rate (TLR) in stretches between snow-free to snow cover area (1.2°C/100 m) is more than the TLR in stretch of continued snow cover. Temperature, snowfall, rainfall and snow depth per 100 m of rise in elevation have been estimated as -1.09°C, 31.2 cm, -7.72 mm and 27.95 cm, respectively. The snowfall and rainfall mixed precipitation occurs within 0.65 and 11.5°C of weekly Tm for which distribution pattern has been developed. Temperature degree-day melt factors, determined in water equivalent term, vary between 2 and 11.5 mm°C-1d-1 and it may rise up to 13 mm°C-1d-1 for non-zero snow condition. The snow depth excess at Solang (2450 m amsl) in relation to Bhang (2190 m) has reduced by 50% over three decades while the snow depth excess at Dhundi (2950 m) from the snow depth at Bhang has increased by 15%. Furthermore, disappearance of the snow cover has been experienced earlier by 5 weeks in the region.

It is widely acknowledged that the statistical properties of precipitation and temperature will change under the future climate condition, and this will cause a significant impact on water resources and its management at watershed scale. This study investigated the hydrological response to climate change for Spencer Creek watershed located in Southern Ontario, Canada. The precipitation and temperature projection used in this study were obtained from the North American Regional Climate Change Assessment Program (NARCCAP) climate simulations. NARCCAP climate projections were bias- corrected for meteorological stations representative of the watershed. The biascorrected NARCCAP climate projections were used as input in a calibrated hydrological model Hydrologiska Byråns Vattenbalans-avdelning (HBV) to simulate flows at the outlet of the watershed. The improvement of bias-corrected NARCCAP precipitation and temperature is revealed by Brier and Rank Probability Skill Score (BSS and RPSS, respectively). The comparison of current and future simulated flow results reveals an increase in winter daily average flows and decrease in other seasons, and approximately 13% increase in annual evapotranspiration under future climate condition. An increase in high flows and decrease in low flows under future climate is revealed by flowduration analysis.

In the present paper the hydrological regime around Sukhna wetland is studied to know how a wetland is functioning, its influence on hydrology of the area and wetland-groundwater interactions. The subsurface geology of boreholes drilled around Sukhna wetland reveals thick zones of boulders, pebbles, gravels, sand and clay at different depths. In this area there are two type aquifer systems i.e., shallow and deep. The depth for shallow aquifer ranged 2-20 m bgl and in deeper aquifers ranged 10 above 40 m bgl. The water level fluctuations for the period 1985-2013, indicates the declining water level trend in both the seasons i.e., pre monsoon (May) and post monsoon (November) due to over exploitation by tubewells installed by the Public Health Department, UT, Chandigarh for providing domestic water supply. The water table elevation contour maps for May and November months in Chandigarh for years 1986, 1991, 1999, 2005 and 2012 reveals that the regional ground water flow direction is from Northeast to Southwest and there in no significant temporal variations in regional ground water flow direction. On the basis of hydrological regime study around Sukhna wetland it is inferred that no appreciable rise in water levels has been observed around Sukhna wetland but it is contributing recharge in the upper shallow aquifer system in the central part of Chandigarh and below as the subsurface groundwater flow is towards south and south west direction

In the Sahara sand dunes extend over large areas and seem to be an obstacle in the infrastructure of the urban development of the Sahara and an ecological barrier called desertification. We are interested in the sand filtration technique, as an essential phase for the water pretreatment, such processes are recognized as well-suited to rural areas, since they have a good quality treatment, a simple and relatively low maintenance operation. Knowing that the region of Bechar (1000 km from the capital) is a sandy area, preliminary work as the sand of Beni Abbes was taken as the filter bed. The goal is the development of this material abandonment in our region. It follows from the work at the laboratory scale, the studied sand has favorable characteristics for their use as filter bed, we can say that it is a fine sandy soil textures of an effective diameter (d10) of 0.17 mm and a uniformity coefficient (Cu) of 1.76, as well as their very low permeability of the sand which is in the range of 7.26 × 10-4 ms-1. Chemical analysis carried out on the overall fraction sand us to provide qualitative and quantitative information on the chemical composition of the sample. The results obtained indicate that the sand sample contains no manganese, the presence of aluminum and calcium iron oxide may be an indicator of the presence of these elements in different forms. Calcium oxide has important levels reached 1.15% and very probably due to the presence of calcite (CaCO3), quartz is the most represented mineral considered insoluble portion 97%.

Water is essential for life and for most activities of human society. Both economic and social development and the maintenance of human health are completely dependent upon ready access to adequate water supplies. All societies require water both for basic survival and for economic development. Limited and inadequate access to water supply for productive uses such as livestock watering, crop irrigation, and small scale industries, constraints households and communities in a condition of vulnerability and poverty. Lack of access to safe domestic, and indeed to significant quantities of water for other productive uses defines and contributes to poverty. Provision of and access to safe domestic water for productive uses will contribute to the Millennium Development target of halving the proportion of people without access to safe and sustainable water supplies by 2015, in addition to contributing significantly to incomes and livelihoods. Groundwater resources thus offer major development of communities. Great socio-economic benefits have been generated by high-quality, relatively low-cost, drought-resilient groundwater supplies for urban expansion, industrial enterprises and agricultural irrigation and with rising population and continuing development in Nigeria, demand for groundwater is still increasing. This paper, therefore opines that it is not simply a matter of having a low or irregular income, but of lacking a wider set of assets-human, social, physical, natural as well as financial and being vulnerable to changes which the less-poor can readily survive. This paper therefore aims at promoting water poverty to water prosperity, outlining and exploring the opportunities and role of groundwater in the reduction of chronic poverty, economic sustainability as well as draws out conclusion for the way forward in Nigeria. The contribution of groundwater to the enhancement of livelihood and in the fight to combat poverty, reduce vulnerability and improve chances of survival is advocated. Overall, groundwater is and will be a reliable water resource for human development for solving water supply issues, improvement in human health conditions and alleviation of poverty.

Soil erosion and the subsequent sedimentation are the major watershed problems in Ethiopia. Removal of top fertile soil, siltation of Koga irrigation reservoir, clogging of irrigation canal by sediment and reduction of irrigated land are the major threat of Koga watershed. Hence, this study was attempted to assess and map the spatial distribution of sediment yield of Koga watershed in a GIS and remote sensing environment. Sediment yield is dependent on factors of soil erosion such as rainfall erosivity, soil erodibilty, land use land cover (C and P) and topography (LS) and sediment delivery ratio of the drainage basin to the total amount of sediment yield by sheet and channel erosion. RUSLE framed with GIS and Remote sensing technique was therefore employed to assess the amount of soil loss existed in KW. Main stream channel slope based sediment delivery ratio analysis was also carried out. Soil map (1:250,000), Aster DEM (30 × 30 m), Thematic Mapper (TM) image (30 m × 30 m) of the year 2013, thirteen years (2000-2013) rainfall records from four rain gauge stations and topographic map (1:50,000) were the major data used. The estimated mean annual SY delivered to the out let of KW was found to be 25 t ha-1year-1. Most critical sediment source areas are situated in the steepest upper part of the watershed due to very high computed soil loss and sediment delivery ratio in this part. It could be therefore difficult to attain the intended goal of Koga irrigation reservoir positioned at lower part of the watershed. Sustainable land management practices have to be conducted in the upper part of the watershed by taking each stream order as a management unit to increase the storage capacity, and/or lessen the transportation capacity of the watershed. Proper drainage construction and stream bank stabilization via vegetative cover have to widely implement to safely dispose the eroded sediment.

The purpose of this study is to provide a better understanding of the impact of different sources of stress (natural and human related) on water quality in a coastal lagoon (Bizerte, Tunisia). Impacts have been assessed through both surface and bottom water samples that were analysed for a range of chemical parameters. Results indicate that nutrient concentrations were generally high throughout the column especially during the rainy season. This period generally corresponds to intensive vertical mixing and massive discharge from rivers inflows. Concentrations were generally relatively high at the surface. The data structure is identified by the first three principal components explaining 68% of the total variance. Cluster analysis showed two different groups of similarity between the sampling sites reflecting the different physico-chemical characteristics and pollution levels of the studied water.

Rivers are highly vulnerable water bodies to pollution due to their roles in assimilating or carrying off the municipal and industrial wastewater and run-off from agricultural land in their vast drainage basins. This paper analyzed the effluents discharged from industries contain chemicals which directly affect the parameters of the water. Present study deals with the investigation of monthly as well as seasonal variations of selected parameters in river Ami, which is a prime river in Gorakhpur, India. BOD 5 test measures the oxygen demand biodegradable pollutants whereas the COD tests measure the oxygen demand of oxidizable pollutants. These tests have its widest application in measuring waste loadings to treatment plants. The maximum value of BOD 5 was recorded to be 188 mg/l while COD was recorded to be 370 mg/l during summer and DO was completely absent during most part of the year.

This project aims to detect variabilities and trends in outputs of a three dimensional hydrodynamical numerical model based on a version of the Princeton Ocean Model (POM), covering the region between 85°S-30°N and 70°W-25°E, with 0.5° x 0.5° resolution. Surface data of temperature and salinity, from Climate Forecast System Reanalysis (CFSR), together with meteorological data of winds and surface fluxes, generated by reanalyzes of NCEP/NCAR global model, were used as model forcings. The temperature-salinity data, meteorological data and model results cover the period from 1980 to 2009 (30 years). The model was validated through comparisons with outputs of oceanic buoy data from the PIRATA project (for the period 1997-2009) and satellite measurements by MODIS sensor (for the period 2003-2009). Model results and sea surface temperature data from PIRATA display strong correlations, both in the annual and higher frequencies signals. Even filtering the annual and semi-annual signals in the surface temperature series, model results and buoy data have mean value of linear correlation 0.59 ± 0.07 and mean value of Wilmott parameter 0.57 ± 0.15. The model results showed a mean difference of temperature to PIRATA series of 0.44 ± 0.26°C, denoting a slight underestimation of the temperatures computed by the model. The comparison of temperature profiles from the model to the PIRATA buoys shows that the model can be considered valid to surface data, but need some improvement in depth. Harmonic and statistical analyzes of selected points, applied to meteorological parameters, sea surface elevation, temperature, salinity and currents provide information on the variabilities and trends in the Tropical and South Atlantic Ocean. As an example, an extremely high trend of surface temperature was found in the Equatorial region and in the latitude belt of 40°S, for the period 2003-2009, reaching above +0.2°C/year. In this period, a trend of -0.01 m/s/year was computed for the equatorial surface currents, surrounded by trends of +0.01 m/s/year off the African coast, at about 3°N and 3°S. However, an analysis in a longer period of time would be needed for more conclusive statements. Analyses of the distributions of the standard deviations show that seasonality is not always the main factor responsible for most of the standard deviation, such as for the intensity of the currents in the equatorial region.

An alternative landfill capping technique ‘Phytocapping’ (establishing plants on a layer of soil placed over the waste) was trialled at Rockhampton, Australia. In this capping trees act as ‘bio-pumps and ‘rain interceptors’ and soil cover as ‘storage’. They together minimise water percolation leading to reduced leachate production. “Transpiration” is a vital process to maintain the hydrological balance of a particular site. To be successful, the trees must transpire enough water from the soil so as to reduce water percolation through the refuse. Water uptake in trees is influenced by plant growth, tree characteristics, root activities, soil depth, soil water availability as well as climatic conditions (rainfall intensity, wind velocity, relative humidity and temperature). The potential of the tree species to remove water from the system plays a vital role in the sustainability of phytocapping system. Currently very little information is available on water uptake patterns of native species established on landfill sites. Results from this study suggest that the tree species grown on a phytocap are able to take up to 2.1 mm day-1 of water with an average of 1.4 mm day-1.

The Techa Cascade of water reservoirs (TCR) is one of the most environmentally challenging facilities resulted from FSUE “PA Mayak” operations. Its reservoirs hold over 360 mln m3 of liquid radioactive waste with a total activity of some 5∙1015 Bq which is about 0.1% of the total radioactivity released from the Chernobyl accident and occupy an area equivalent to roughly the size of 7,000 football fields. A set of actions implemented under a special state program involving the development of a strategic plan aimed at complete elimination of TCR challenges (Strategic Master-Plan for the Techa Cascade of water reservoirs) resulted in considerable reduction of potential hazards associated with this facility. The report summarizes the key elements of this master-plan: defining the facility’s final state, feasibility study of the main strategies aimed at its attainment, evaluation of relevant long-term action plans, development of computational tools enabling the long-term forecast of TCR behavior depending on various engineering solutions and different weather conditions.

The behavior of metals in surface water is complex and their partition coefficients can be impacted by many factors. Organic matter (OM) content in sediments, pH and salinity, are factors that may influence speciation and partitioning of metals. The difficulty in describing the impacts and relationships are that these processes are interconnected with no dominant associations among all. In this study, the partitioning of five metals (As, Cr, Cu, Ni and Zn) under different levels of salinity, pH, and OM content were investigated. A series of factorial design experiments are evaluated in which three levels of OM are tested each time against five levels each of salinity and pH; the design of experiments was generated by the statistical software program MiniTab16®. All metals tested showed a trend of increasing Kd with the increase of OM 0.36% to 4.32%. Higher Kd were the result of the increase in pH from 3-10.5 and lower Kd values resulted after an increase in salinity 0-3%. However, within that lower range of salinity, a positive linear correlation between Kd and salinity was observed which is attributed to potential formation of insoluble metal species with the increase of salinity. Multiple regression equations with the variables pH, OM and salinity were generated to predict Kd of each metal. The study showed no interaction between salinity/OM and pH/OM for all five metals.

Using Bio-sphere Atmosphere Transfer scheme (BATS) coupled regional climate model (RegCM4) the impact of intensification of irrigation on Indian monsoon atmospheric circulations and surface fluxes is being studied. Land use/land cover change is performed in the model to study the design or sensitivity experiments. This is implemented by changing the vegetation/landuse type in the model. Impact of increase in irrigation activity over Central India and Northwestern region of India is still an open question and hence it is attempted to answer them in this research work. In the first irrigation sensitivity experiment, vegetation/land-use types have been modified to “irrigated crop” type along districts of Central India, Indo-Gangetic plain and northern parts of India, in the RegCM4 model to test the hypothesis that whether-“increase in irrigation decreases monsoon (JJAS) precipitation over certain regions of India and increases pre-monsoon (MAM) precipitation”. Simulations suggest that increase in irrigation over Indian monsoon domain has altered the Indian summer (JJAS) monsoon by weakening it at regional scale over various regions due to probable weakening of the temperature contrast between land and sea. Increase in irrigation over the central India causes a decrease (increase) in sensible heat flux (latent heat flux, surface pressure) in summer monsoon season. To further test the hypothesis that the northwestern region of India is a hotspot for land atmosphere interactions and to test the impact of irrigation intensification over northwestern region of Indian subcontinent, on Indian summer monsoon another sensitivity experiment with irrigation intensification over northwestern regions of India is performed using RegCM4. This experiment suggests that irrigation impact or sensitivity on soil moisture; surface fluxes are limited to northwestern region of Indian subcontinent. Simulations performed at higher (50 km) resolution shows increase in precipitation during pre-monsoon season over northwestern regions of India, too. The Indian monsoon circulations are a part of global general atmospheric circulations periodic in nature and any form of vegetation impact study is a complex process. Thus, from the irrigation sensitivity experiments (using a regional climate model) it can be concluded that due to increase in irrigated land over India, pre-monsoon (MAM) precipitation increase particularly over Central and northwestern regions of India, with the development of anomalous cyclonic circulations.