நீரியல்: தற்போதைய ஆராய்ச்சி

Phosphorus (P) is a vital nutrient for plants, however its excess loss from agricultural lands cause eutrophication on aquatic environment. The Gilgel gibe reservoir located in the southwest part of Ethiopia is exposed to this phenomenon whereby the water quality has been classified as mesotrophic with P concentration of 0.86 mg/l. The objectives of this study were to identify the operating P loss mechanisms from agricultural lands, quantify the amount of P exported and evaluate the factors for P loss using the best management practices (BMPs) concepts. Therefore, experimental data and the annual phosphorus loss estimation (APLE) model were used to study the underlying processes. Catenas surrounding the reservoir, used as arable and pastureland, were investigated. Topsoil samples were taken and analyzed at three slope positions. The soils are mainly nitisol and a smaller portion of vertisol where the parent materials are basalt and rhyolite. The APLE model was set using soil data from the arable lands with nitisol soil and hydrologic records. The phosphorus loss was simulated from 2001 to 2010. Besides, the experimental P sorption data were used to check the logical consistency of the model output. On average 12.66 ± 0.7 kg P ha-1 yr-1 is lost in the form of particulate and total dissolved P. Generally, 56% of P is lost in the form of particulate P due to erosion, and 44% as soils dissolved and direct fertilizer runoff P. A significant variation observed between the sediment and soil dissolved P loss (p-value= 0.000) which is attributed to the soil chemical and physical properties that control the phosphorus dynamics. Obviously the dominant P transfer from agricultural lands into the Gilgel Gibe River and reservoir is particulate P loss. An evaluation of causing factors using BMPs indicated that a reduction of sediment by 5-20% resulted to retain P from 2-9%. Similarly, a reduction of soil P content reduces the P loss from 2-8.5%. However, a reduction of fertilizer quantity applied on the fields within the same percent range is hardly reducing P loss relative to the earlier factors. Therefore, attention should be given to the application of precision agriculture to avoid such problems.

This study using a regional climate model, ICTP-RegCM4.0 simulations examines the impact of drying and shrinking of Caspian Sea on Indian summer and winter monsoon, particularly on precipitation over northern plains of India due to Western disturbances. Shrinking of Caspian Sea is a man-made catastrophe with serious environmental implications. To perform the sensitivity experiment the original landuse map in the model is altered where the “Caspian Sea” in Central Asia is changed to “semi-desert” in place of “inland water” type of vegetation. The model is forced with NNRP2 boundary conditions for year 2009, 2010. Analysis of sensitivity experiment output w.r.t baseline experiment says that rainfall over Northern India decreases (significant at 5% level), during the months of winter season (months of October to March) primarily from Western disturbances originating from Central Asia and Caspian Sea region. Also, it is found that minimum (maximum) temperature decreases (increases) particularly over Indian region during October to March and June to September. During June to September (for year 2009, 2010) from model simulations results it is found that over Central Asia (India) air temperature extending upto 700hPa increases (decreases).

Evaluation of land use land cover changes on the hydrological regime of river basins is one of the concerns in the global climate change. With plethora of tools available in the literature choosing of an appropriate tool that can quantify and analyze the impact of land use land cover changes on the hydrological regime in a systematic and planned manner is important. Soil and Water Assessment Tool (SWAT) integrated with Geographic Information System (GIS) based interfaces and its easy linkage to sensitivity, calibration and uncertainty analysis tools made its applicability more simple and has great potential in simulation of the past, present and future scenarios. A number of standards were used to appraise the model set-up, model performances, physical representation of the model parameters, and the accuracy of the hydrological model balance to assess the models that are defined in journal papers. On the basis of performance indicators, the mainstream of the SWAT models were categorized as providing satisfactory to very good. This review debates on the application of SWAT in analyzing land use land cover changes in semi-arid environment. Application of SWAT and land use land cover simulation models for impact assessment in semi-arid region improves accuracy, reduces costs, and allows the simulation of a wide variety of conservation practices at watershed scale. It is also observed that different researchers and/or model versions bring about in different outcomes while a comparison of SWAT model applications on similar case study was applied. This review determines the interactive role of SWAT and GIS technologies in improving integrated watershed management in semi-arid environments.

The use of micro organisms for heavy metal remediation in water is a technique widely studied. This review describes a number of methods used for Acid Mine Drainage (AMD) remediation, containing high concentration of this type of contaminant. The AMD is a problem generated in abandoned mines and low grade stock of active mines, therefore it is an existing problem in mining countries. In this review it is described the problem in Chile, regulations and the challenge to resolved this problem for a sustainable industrial future.

Piggery waste is one the tree major water pollution sources in Taiwan. Piggery waste should be viewed as resource and not waste. Conventionally, three stage wastewater treatments are too costly and hard to operate. Direct application to soil can be a remedy if the application rate is careful managed. Taiwan EPA ambitiously launches piggery manure direct apply to soil policy. It might the panacea to water pollution control.

This paper analyzed the spatial-temporal variations of surface water quality along the middle and lower reaches of the Min Jiang between 2003 and 2012 and investigated its pollution sources by analyzing the data from 4 water quality monitoring stations. The results showed that surface water quality was higher polluted in the middle reaches of the Min Jiang than that in the lower reaches and its tributary. Seasonal and spatial differences were found for DO, CODmn and NH3-N, whereas for TP the differences were mainly due to the water quality station. The level of organics (CODmn) was higher in summer (high flow period), and the level of NH3-N was higher in winter (low flow period). In the middle reaches of the Min Jiang, point sources (from wastewater treatment plants and industrial effluents) were found to be the dominant inputs of organics (CODmn) and nutrients (NH3-N and TP) to river. In the lower reaches of the Min Jiang, diffuse sources (from agricultural fertilizer, soil erosion, etc.) were the dominant contributor of organics and TP to river, while point sources were the dominant input of NH3-N. In tributary, diffuse sources were the dominant organics and TP input, both point and diffuse sources were dominant NH3-N inputs. Overall, these results reinforced the notion that pollution control by periods and regions was important for effective water quality management, and it is necessary to enhance the treatment of industrial effluent, to strictly carry out the discharge standard for water pollutants and the total amount control system, to incorporate NH3-N in the total amount control system in the Min Jiang.

The growth of population and its effect on the land use-cover change have been influencing the hydrology of the sub basin by changing the magnitude of stream flow and groundwater flow. In this paper, the likely land use-cover change impacts on hydrology of the Melka Kuntrie sub basin in the Upper Awash River Basin have been evaluated using the semi-distributed HBV hydrological model and Landsat imageries for two different periods. ArcGIS was used to generate the land use-cover maps from Landsat 5 TM and 7 ETM+ acquired, in the year 1986 and 2003, respectively. The land use-cover maps were generated using the Maximum Likelihood Algorithm of Supervised Classification. The accuracy of the classified maps was assessed using contingency matrix. The result of this analysis showed that the cultivated land has expanded from 1986 to 2003. The land use in 2003, which was mostly converted to agriculture land from forest, grass, or shrub land, showed an increased stream flow in the main rainy season, while the stream flow in dry or small rainy season indicted inconsistency from month to month. In the same time, there was a decrease in evapotranspiration in 2003 land use. The stream flow increased by the 2003 land use was 25% in June, 4% in July, 6% in August and 9% in September that corresponded to 0.065 mm/day in June, 0.077 mm/day in July, 0.07 mm/day in August and 0.039 mm/day in September for the main rainy season as compared to the 1986 land use. The model calibration was carried out using observed hydrometeorological data from 1991 to 2004 and the validation period was from 2005 to 2008. The performance of the HBV model for both calibration and validation was reasonable well and the Nash-Sutcliffe efficiency was 0.86 and 0.78 for calibration and validation, respectively.

The major problem in the study area is the unlawful water abstractions for irrigation use. In South Africa, indications show that about 240 million m3/a of illegal water use is due to unauthorised withdrawals or violations of water use licenses. The status of water use for irrigation in the Orange-Senqu Basin also shows that insufficient information exists such that work needs to be done to understand the potential for increased efficiency of water use, taking into account issues pertaining to crop type, soil type and technological options. Studies like this one could also shed light on the potential impact of climate change on water use in the basin as this area may well experience significant impacts from rising temperatures and changing rainfall patterns. The processes of validation and verification will determine the extent of existing lawful water use. The use of remote sensing techniques (satellite, aerial photographs, etc.) could be employed to determine if the volume of water use registered by irrigators is accurate, i.e. valid and that the volume of water use registered is lawful (verification). Currently, ecological requirements for the river mouth are met through releases from Vanderkloof Dam and amount to just 290 million m3/a. However several recent studies including the Gesellschaft für International Zusammenarbeit - Integrated Water Resources Management (GIZ – IWRM) study highlight that this is based on a fairly outdated methodology. The more recent Lower Orange Management study found a high level estimate of ecological requirements to be in order of 1 062 million m3/a.

The paper addresses uncertainties that emanate as a result of methods used to determine irrigation areas in the Upper Orange River catchment area. The largest water user is the irrigation sector. What is not known for all schemes are the return flows but an average estimation of 13% is done for the main irrigation areas. Though several previous studies have addressed water conservation and demand management in the in the Orange-Senqu River catchment area; some pitfalls/caveats remain identified by these studies pertaining to the practical implementation of results. It was the necessary to look into several methods used since the results produced, in some instances differed so much. An establishment of a standard methodology for the collection of data on irrigation water applied to crops, water use by crops and crop yields is a necessity. Establishment of an inventory GIS Database for irrigation inventory could prove useful if it could enhance the collation and collection of detailed and reliable data about irrigation water use by crops and crop yields. It could lead to documenting best management practices for irrigation in the catchment area. Another path could be to assess and consider various instruments that could be used for water conservation and demand management and further made improvements on water conservation and water demand management (WC/WDM) in the sector.