A highly pathogenic avian influenza virus, H5N1, caused disease outbreaks in poultry in China and seven other east Asian countries between late 2003 and early 2004; the same virus was fatal to humans ...in Thailand and Vietnam. Here we demonstrate a series of genetic reassortment events traceable to the precursor of the H5N1 viruses that caused the initial human outbreak in Hong Kong in 1997 and subsequent avian outbreaks in 2001 and 2002. These events gave rise to a dominant H5N1 genotype (Z) in chickens and ducks that was responsible for the regional outbreak in 2003-04. Our findings indicate that domestic ducks in southern China had a central role in the generation and maintenance of this virus, and that wild birds may have contributed to the increasingly wide spread of the virus in Asia. Our results suggest that H5N1 viruses with pandemic potential have become endemic in the region and are not easily eradicable. These developments pose a threat to public and veterinary health in the region and potentially the world, and suggest that long-term control measures are required.
Abstract The Katingan I Lowlands Irrigation Area (LIA) is one of tidal lowlands irrigation area in Central Kalimantan, Indonesia. Because the Katingan I LIA utilizes water from the estuary, the ...occurence of saltwater intrusion is likely to occur. Assessing water salinity due to saltwater intrusion provides essential information for farmers to manage water appropriately. In addition, this information can also be used by the government to develop policies and management strategies for Katingan I LIA. Saltwater intrusion that occurs when sea water flows into irrigation canals and agricultural land can lead to increased salinity. High salinity levels can affect agricultural productivity, especially in rice crops. Therefore, a thorough salinity study is needed to support the development of rice farming. This study aims to evaluate salinity levels due to saltwater intrusion and understand the factors affecting them. The study measured tidal (water level elevation), electrical conductivity (EC), and salinity data of the Katingan River and several locations in the primary and secondary channels. Data collection methods included continuous and instantaneous measurements using portable data logger installations and handheld devices. The existing water salinity conditions at Katingan I LIA obtained the maximum water salinity value from the three locations of 14,536 ppm and the lowest water salinity value of 3.02 ppm. The maximum water salinity value that enters the primary canal is 5,547 ppm, higher than the thershold salinity value for rice farming (5,120 ppm). Therefore, anticipatory measuers must be conducted to reduce salinity intrusion, such as optitmizing water channels, making water gates, and managing the water use efficiently. It is also recommended that measurements be carried out during the dry season to see the comparison of results and the magnitude of the maximum water salinity value that occurs because salinity problems occur more during the dry season
Abstract The Katingan I tidal lowland irrigation area (DIR Katingan I) is a sensitive area to salinity changes. This study aims to identify and estimate the spatial distribution of salinity in DIR ...Katingan I. The method used in this study is field measurement for collecting tidal and salinity data in the Katingan River as well as in several locations of primary and secondary canals. The measured data at the upstream canal, Katingan River, and primary canal as boundary conditions and calibration for hydraulic and water quality simulations. The simulations used HEC-RAS software to estimate salinity spatial distribution under tidal conditions at primary and secondary canals. The results showed that the distribution of water salinity can reach lower primary canals. It is necessary to take anticipatory actions to reduce the salinity intrusion. To overcome the problem, alternative recommended solutions that can be done are sluice gates installation on the lower primary canal, right primary canal, and left primary canal about 1 to 3 km from the mouth of the primary canal. The prediction of salinity spatial distribution is expected to be a useful recommendation for water management in DIR Katingan I, and it is expected to increase agricultural productivity.
Abstract Rice fields in the Katingan tidal lowlands are inundated due to spring tides and extreme rainfall. Excessive inundation in the rice fields causes crop failure. Therefore, the study was ...conducted to analyze the use of water gates in the secondary canals for controlling the inundation. The unsteady flow simulation boundary conditions are the upstream discharge with a return period of 5 and 25 years and measured tidal. The water flow is controlled by closing the sluice gates at the water level elevation of +3.50 m, and flap gates close during high tide and rainfall. This research shows that controlling the water flow by gates decreases the water level and inundation area. Under rainfall with a return period of 5 years, the inundation area decreased by 79.03 %, and the maximum water level decreased by 0.14 m. In the rainfall with a return period of 25 years, the inundation area decreased by 75.31%, and the maximum water level decreased by 0.11 m. The water gates’ operation incompletely decreases the inundation and water level beneath rice crops’ threshold inundation depth and duration. Therefore, there is a need for additional water control to optimize the decrease of inundation in the rice fields.
Abstract A phenomenon in which non-cohesive soil in saturated conditions loses its carrying capacity owing to the reduced stiffness and strength of the soil during earthquake shaking or rapid loading ...is called liquefaction. This occurs under the structure and can cause damage during earthquakes. In this study, we estimated the possibility of liquefaction in the main irrigation canals in the Sibowi area of Central Sulawesi Province, considering that the soil type in this area is sandy. Liquefaction analysis uses a simplified procedure using Standard Penetration Test data to obtain the Safety Factor and estimate the potential level of liquefaction using the Liquid Potential Index (LPI) method. According to the analysis, with the 7.5 Mw earthquake and groundwater levels observed, most of the soil layer below the irrigation canals still has liquefaction potential at 15 m to 19.5 m. The LPI result that 5 (five) out of 10 (ten) boreholes have the potential for liquefaction in low to moderate categories, and the boreholes that have liquefaction potential have groundwater depths between 14 and 16 m.
Abstract
This study aims to understand the flow and water quality behaviour in response to the combination of rainfall and tides in the Dadahup Irrigation Area. Rainfall and tides have a strong ...influence on the Dadahup Irrigation Area. The impact of floods and droughts which hit the area in recent years changed its water quality because of salinity intrusion and the presence of pyrite in the irrigation area. The existing gates and levees along the main primary channel cannot fully regulate the water level on the other channels and on the paddy fields. This condition has resulted in crop failure in several places. Parameters of flow and water quality data such as rainfall, water level, pH, and salinity were measured from an newly installed telemetric monitoring system. A sampling period was selected in which both rainy and dry conditions were present. In that period, tides also oscillated the water level. Hydraulic simulations will analyze the hydrodynamic condition along with the observation results and will describe the flow profile and water quality changes. Simulations show that a high-intensity rainfall can immediately raise water levels in the main primary channel, and it impacts increasing pH and decreasing salinity.
Belanti II tidal irrigation network was developed in 1980 on acid sulphate soil with an area of approximately 3976 ha. Belanti II has one primary channel and several secondary channels, without any ...water structures that regulate the direction of flow. Two-way flow occurs in the channel, supplying fresh water from the river at high tide and flowing back into the river at low tide. This two-way flow system inhibits the leaching process of acid sulphate soil. Up to now, acid sulfate soils are still found at a depth of 50-75 cm with a pH of 2.5 ~ 3.5. A one-way flow system is expected to improve water circulation, assisted by channel rehabilitation, collector channels and water control structures. The spillway structure at the secondary channel regulates the freshwater supply at high tide and the flap gate at the end regulates the flow of water to the collector channel at low tide. Hydraulic analysis was carried out using HEC-RAS modelling. The results showed the ability of the system to supply fresh water, flushing/leaching acid sulfate water and drainage the toxic water. The effectiveness of the system is evaluated regarding the direction and the volume of freshwater flowing into the secondary channel.
Abstract Equilibrium and non-equilibrium sediment transport flow in natural rivers and artificial channels can result in degradation or aggradation of the river bed, which will affect many hydraulic ...parameters, one of which is shear velocity. This study evaluates the influence of sediment transport on shear velocity in open channels. In this study, laboratory experiments were carried out using a sediment-recirculating flume, and measurements of the velocity and Reynolds shear stress distributions were measured using a Sontek-acoustic Doppler velocimeter (ADV). This experimental study measured 120 velocity distributions, and Reynolds stress profiles, consisting of 12 different sets of measurements involving flow with sediment transport and movable sand bed. The results showed an average shear velocity, u* , difference between sediment feeding and without sediment feeding by 9.41%. For the integration constant Br value, the average difference between sediment feeding and without sediment feeding was 5.58%.
Abstract
Sei Teras fishpond area was developed by the Banjar community in 2006. The conditions of the ponds in Sei Teras are still very simple, where the availability of seeds and feed is completely ...dependent on nature. The evaluation is based on the level of control and the production rate, while efforts for improvement are planned through controlling water quality. In the rainy season, the shrimp productivity ranges from 180 Kg/ha, while it can reach 450 kg/ha in the dry season. From the measurements results in November 2020-Mei 2021, it was noted that the salinity of the water in fishponds and canals ranged from 2 to 24.3 ppt while the water pH ranged from 6.11. to 7.87. Water quality parameters such as DO and pH have met the criteria for applying higher aquaculture technology, while other parameters such as Nitrate, Nitrite, Ammonia, TDS and Salinity require improvement and/or control. An alternative design is in the form of rearranging the fishpond system such as individual fishpond size. In addition, it is necessary to manage the fishpond irrigation network, namely by planning the main control structures separating fresh water and saline water, and rehabilitation of channels that experience sedimentation.
Abstract
Flash flood is defined as “a flood of short duration with a relatively high peak discharge,” which leaves little time to take action to reduce property damage and the risk to life. Flash ...floods occur not only because of heavy rainfall but some co-factors that can trigger it. This study aims to determine the co-factors that trigger the flash flood. Observations are carried out using a descriptive-qualitative approach of five small catchments in Indonesia, namely Bahorok Catchment (Langkat, North Sumatra), Kalijompo, and Kalipakis Catchment (Jember, East Java), Nasiri Catchment (Western Seram, Maluku), Wasior Catchment (Wondama Bay, West Papua). The dominant co-factors are related to rainfall IDF, morphological characteristics (slope, channel properties, flow pattern), geological conditions (rock, soil, structure, geohydrology), catchment conditions (vegetation, land use). Flash floods generally occur due to landslides in the upstream part of the river. Debris consisting of water, rock, and tree trunks can stem the river’s flow and form natural dams. In five flash flood cases under investigation, the causes of a flash flood triggered by heavy rainfall and the morphological characteristics are 60% and 40%, respectively. The quantitative measure of each co-factor that triggers flash floods is essential for further research to identify flash flood symptoms.
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