நீரியல்: தற்போதைய ஆராய்ச்சி

A bifurcated fiber-optic light guide was used to measure the colors of clays in a groundwater stream over the Upper Ordovician Queenston Formation of the Niagara Escarpment (Ontario, Canada). One branch of the light guide illuminated the samples, and the other branch gathered reflected light for spectrophotometry. Measuring Munsell rock color chips, and using the weighted-ordinate method to calculate chromaticity coordinates from reflectance spectra, the dominant chemically reduced clay was greenish-gray (Munsell 5G 6/1, x=0.348, y=0.352, Y%=62.3) while the dominant oxidized clay was grayish-red (Munsell 5R 4/2, x=0.388, y=0.338, Y%=23.8). The electrical impedance of clays was correlated with x (r=-0.92 for capacitance and r=0.96 for resistance, P<0.001 at 10 kHz). The peak wavelengths for correlations were around 500 to 540 nm. The matrix between the corallites of a Devonian fossil coral above the collection site (Eridophyllum seriale) was within the statistical range of oxidized grayish-red Ordovician shale. There was no evidence that low pH in the groundwater stream had caused the variation in clay color, thus, leaving conditions when the source shale was deposited as the most likely cause of color variation.

This study shows the impact of hydro climatic variability on water resources in the Lake Chad watershed. The application of Nicholson and Maillet methods and statistical tests for homogeneity (Buishand's, Hubert's, Lee and Heghinian's and Pettitt tests) made it possible to demonstrate a climatic variability characterized by alternation Wet, normal and dry season with a long deficit period that began around 1977 and resulted in an impoverishment of water resources in Chad. This decline in rainfall decreases the flow of water that passes through the Lake Chad basin. According to the Buishand test, this decrease in water level is marked by a very significant break, which oscillates between 90% and 95% in the years 1982 for the stations assumed in the center of study area such as Moundou and Bousso. The study found that in the 1960s Lake Chad covered an area of 25,000 km2, under the combined effect of climate change, its surface area shrank to 2,500 km2 in 2004. This hydro-climatic variability has a negative impact on agricultural, pastoral and fisheries activities and is a major threat to the population living around this basin. The results of this study showed that large variations in water levels and landscapes are directly dependent on rainfall in the Chari basin and it is possible to indicate that agricultural production, access to food in the years to come, be seriously compromised by climate change resulting in wide variability in the availability of water resources.

The hydrological investigations are fundamental to infrastructure development including roads, bridges and other social facilities. The rainfall-runoff analysis is central to all such hydrological analysis. Rainfall excess values are often used as input to various hydrological models for the designing of various hydraulic structures such as bridges, culverts, spillways and flood control works of all sort. This part has more uncertainties due to a complex nature of the watersheds and normally requires calibration of parameters involved in such relationships generally imperial in nature. Under the current study, an attempt has been made to evaluate an appropriate excess rainfall method by carrying out a comparative study on local catchments in Mangla watershed of Pakistan. Four methods namely 1) Initial and uniform loss rate 2) Exponential loss rate 3) SCS curve number, and 4) Holtan loss rate have been evaluated in the study, using HEC-1 computer package. A comparison has been made to see which method is the most effective method, applicable to the catchments for which parameters were optimized and also for other similar catchments. The study has been carried out on four different locations located in the same hydrological region. It has been concluded that Exponential method of rainfall excess is suitable for local conditions for catchments ranging up to 100 square miles. For larger areas, a catchment should be divided into sub-catchments for effective results. For a different catchment whether physically similar and located in a same hydrological region, a different set of optimized parameters is required.

Calibration and validation of process based hydrological models are two major processes while simulating the water balance components of watershed systems. However, these processes need a better understanding of the parameters which influence hydrologic processes within the system. In this study, we used SWAT model to simulate the stream flow for Skunk Creek (SK) watershed in South Dakota for the period from 1980-2000. Model calibration and validation were performed for both daily and monthly time periods using SUFI-2 within SWAT-CUP using 24 parameters selected from past available literature. Our calibration outputs for the period from 1987-1994 showed a good correlation between observed and model simulated values with NSE=0.56 and R2=0.70 for daily simulation. However, the model showed a better performance for monthly simulation with NSE and R2 values of 0.84 and 0.84 respectively. During validation period (1995-2000), the NSE and r2 values were 0.55 and 0.44, respectively for daily simulation and these statistical values were 0.76 and 0.77, respectively for monthly time step. Following calibration, the overall effect of each parameter used was ranked using global sensitivity function within SWAT-CUP. From the analysis, SOL_AWC was found to be the most sensitive parameter with absolute t-value of 17.50 and p-value of 0.00 to simulate the stream flow of the SK watershed. The CH_K2 was observed as the least sensitive parameter with t-statistic and p-value of 0.02 and 0.97, respectively. It was concluded from the study that coupling of the SWAT and SWAT-CUP made the calibration process quicker and reliable to simulate local hydrology within the watershed.

Magdalena River is a superficial water body from Colombia, which flows into the Caribbean Sea. Dragging with it elements with diverse chemistry nature throughout the watercourse. Similarly, one of its most flowing current arm of the river, known as the Dique Channel, capture minerals, organic matter, clays and metals. Both Magdalena River and Dique Channel finally slop their water stream into the coast of Barranquilla and Cartagena bay, respectively. The presence of metallic species in dynamic aquatic structures e.g., rivers) and coasts that interact inwardly (sediments-atmosphere-water) triggers variations on the densities from heavy metals existing onto the water. Due to the heavy metal fluctuations given in estuary and marine systems, the annual behavior of Pb, Cr, Cu and Total Hg from Dique Channel was determinate during 2006-2010. The aim of this study is to complement the tracing made by the North University on 2006 and the information related to heavy metals and reports of the physical-chemistry variables given by the Dique Channel Regional Autonomous Corporation-CARDIQUE by means of its participation in the Network for the Monitoring of Environmental Quality of Marine Program-REDCAM. One of the main contributions of the present study is the purpose of control solutions to mitigate the presence of unacceptable concentrations of heavy metals that can jeopardize the flora and fauna from the impacted ecosystems. Results obtained shows that the Canal del Dique drags heavy metals in high concentrations, which can affect dramatically the intern Bay of Cartagena de Indias.