Seasonal Spatio-temporal Land Cover Dynamics in the Upper Brantas Watershed

Quantitative assessment for sustainable watershed management is essential. Hydrological parameters such as stream discharge, surface runoff, infiltration, groundwater recharge, and water quality are susceptible to the changes of the components in the river basin ecosystem. Numerous studies have shown that the Land Use Land Cover (LULC) changes such as deforestation, extensive agriculture, urbanization, and mining are recognized as the main factors to changes in LULC, which are related to the changes of the hydrological components of the river basin of all scale. This paper particularly shows the spatiotemporal variability of LULC in the Upper Brantas Basin and the effects on the river discharge variation. We showed that the changes in LULC, particularly cultivated and managed vegetation and urban/built-up area, contributed significantly to the river discharge. Particularly in the Upper Brantas Basin, it was indicated that almost half of the increased river discharge was explained by the increase of urban/built-up and the decrease in cultivated and managed vegetation area.

Effect of Discharge on Hatching and Growth of Age-0 Black Bass in Two Southeastern U.S. Rivers

We examined the influence of variable discharge on hatching and age-0 growth for fluvial specialist and habitat generalist species of black bass Micropterus spp. in two southeastern U.S. rivers, the Flint River, Georgia (unregulated), and the Tallapoosa River, Alabama (regulated by several hydropower dams). Between 2008 and 2010, we collected 285 Largemouth Bass M. salmoides (generalist) and 254 Shoal Bass M. cataractae (specialist) from two reaches of the Flint River. In 2010–2011, we collected 309 Alabama Bass M. henshalli (generalist) and 216 Redeye Bass M. coosae (specialist) from two regulated reaches and one unregulated reach of the Tallapoosa River. Successful hatching of black bass in both rivers generally occurred from late March to early June when water levels were low and stable. Hatching distributions of all black bass were generally unimodal with little evidence of spawning disruption, except for Alabama Bass in the most-regulated reach of the Tallapoosa River, which appeared to be disrupted by large discharge events. Mean growth of both species in the Flint River varied from 0.64 to 0.82 mm/d across reaches and years; Shoal Bass generally grew faster than Largemouth Bass in all reach–year combinations. Largemouth Bass growth was inversely correlated to discharge variation in one reach, but Shoal Bass growth was not correlated to discharge variation in either reach. Alabama Bass and Redeye Bass growth rates in the Tallapoosa River were similar to rates observed for congeners in the Flint River; Alabama Bass grew faster than Redeye Bass. Growth of both species was inversely related to discharge variation in five of six reach–species combinations; the only exception was for Redeye Bass in the less-regulated reach. Results from this study suggest that variable discharge has less influence on successful reproduction of black bass than was reported for other fishes, but growth may be more affected by discharges resulting from anthropogenic sources than those associated with the natural regime.

Using four different approaches to separate the effects of climate change and human activities on sediment discharge in karst watersheds

<p>Quantifying the relative contributions of climate and human activities to changes in sediment discharge is closely related to regional water resources, soil management and even the healthy operation of ecosystems. However, few studies used different methods to decompose influences of climatic variability and human activities on sediment discharge change, especially in karst regions of southwest China where experiencing severe soil erosion. This study systematically reviewed four different methods including simple linear regression method, double mass curve method, sediment identify factor analysis, and elastic coefficient method to separate the contribution of climate change and human activities to sediment discharge variation in four karst watersheds of southwest during 1955 to 2015. The trend and abrupt change year of sediment discharge in four watersheds were obtained by nonparametric Mann-Kendall test. Result showed that the sediment discharge in four watersheds all decreased significantly (<em>P</em><0.05), and the abrupt change years were 2003, 2003, 2004 and 2004 for Wujiang, Yujiang, Hongshui, and Xijiang watersheds, respectively. The simple linear regression method, double mass curve method and elastic coefficient method all indicated that the sediment discharge was mainly influenced by human activities, with the contribution rate ranging from 73% to 101%. For the sediment identify factor analysis method, the sediment concentration is the principal factor influencing sediment discharge variation, and the contribution rate of sediment discharge varied from 100% to 154%. The results can provide good reference value for evaluating the influence of the climate and human activities on sediment discharge, and is significance for proper formulation of regional soil conservation policy in karst watersheds.</p>

Effects of uncertainty in determining the parameters of the linear Muskingum method using the particle swarm optimization (PSO) algorithm

The Muskingum method is one the simplest and most applicable methods of flood routing. Optimizing the coefficients of linear Muskingum is of great importance to enhance accuracy of computations on an outflow hydrograph. In this study, considering the uncertainty of flood in the rivers and by application of the particle swarm optimization (PSO) algorithm, we used the data obtained from three floods simultaneously as basic flood to optimize parameters of linear Muskingum (X, K and Δt), rather than using inflow and outflow hydrographs of a single basic flood (observational flood), and optimized the outflow discharge at the beginning of flood (O1) as a percentage of inflow discharge at the beginning of flood (I1). The results suggest that the closer inflow discharge variation of basic flood to the inflow discharge variation of observational flood, the accuracy of outflow hydrograph computations will increase. Moreover, when the proposed approach is used to optimize parameters of X, K and Δt, the accuracy of outflow hydrograph computations will increase too. In other words, if rather than using a single basic flood, the proposed approach is applied, the average values of mean relative error (MRE) of total flood for the first, second, third and fourth flood will be improved as 31, 13, 39 and 33%, respectively.

The Influence of Watershed Morphometry to River Discharge Variation (Case Study of Bengkulu Watershed, Indonesia)

Morphometric analysis in a watershed is a requirement in analyzing hydrological conditions in a watershed, because the properties of river networks and their relationship to each other will affect the condition of water resources in the watershed. This study aims to analyze the variations in the discharge of two rivers in the upper Bengkulu watershed and the morphometric aspects that influence it. For this reason, several morphometric aspects are calculated, such as the area of the watershed, circulation ratio, median elevation and slope. The results showed that the Rindu Hati River had a higher monthly discharge than the Susup River. The sizeable difference in discharge between the Rindu Hati and Susup Rivers is due more to differences in the size of the area. As is known, the total area of the Rindu Hati Sub-watershed is 184.2 km2, while the Susup Sub-watershed is 103.6 km2. With a large area, the Rindu Hati Subwatershed will be able to accommodate a large amount of rainwater as well.

Discharge sensitivity of collapsible drip tapes to water temperature

ABSTRACT The objective of this study was to quantify the effect of water temperature variations on the discharge of collapsible thin-walled drip tapes with integrated non-pressure-compensating emitters. The tests were conducted in the laboratory using an automated test bench. Tests were performed to determine the discharge-pressure curves by varying the water temperature from 20 to 50 °C. Nine emitter models of three wall thicknesses (6, 8, and 9 MIL) were evaluated. The coefficients K and x of the discharge-pressure curves varied according to the water temperature. In flat emitters of turbulent flow (x < 0.5), the discharge decreased as the temperature increased. In the welded emitters of turbulent flow, several responses were observed. Regarding emitter D (x > 0.5), the discharge increased as the temperature was increased, while for emitter C (x < 0.5), the discharge decreased; the highest discharge variations occurred at pressures higher than 60 kPa. For embossed emitters, the discharge increased as a function of temperature, however, the greatest variation occurred at the lowest pressures. None of the emitters showed significant difference in the discharge variation due to wall thicknesses.