Simulated impacts of irrigation on evapotranspiration in a strongly exploited region: a case study of the Haihe River basin,China

Irrigation is the major water supply for crop production in water‐limited regions. However, this important water component is usually neglected or simplified in hydrological modelling primarily because information concerning irrigation is notably difficult to collect. To assess real effects of irrigation on the simulation of evapotranspiration (ET) in water‐limited region, the Community Land Model version 4 was established over a typical semi‐humid agricultural basin in the northern China – the Haihe River basin. In the irrigated cropland, incorporating an irrigation scheme can enhance the simulated ET and improve the simulation of spatial variability of soil moisture content. We found that different configurations in the irrigation scheme do not cause significant differences in the simulated annual ET. However, simulated ET with simulated irrigation differs clearly from that with observed irrigation in mean annual magnitude, long‐term trend and spatial distribution. Once the irrigation scheme is well‐calibrated against observations, it reasonably reproduces the interannual variability of annual irrigation, when irrigation water management is relatively stable. More importantly, parameter calibration should be consistent with the configuration of the source of irrigation water. However, an irrigation scheme with a constant parameter value cannot capture the trend in the annual irrigation amount caused by abrupt changes in agricultural water management. Compared with different remotely sensed ET products, the enhancement in the simulated ET by irrigation is smaller than the differences among these products, and the trend in simulated ET with the observed irrigation cannot be captured correctly by the remotely sensed ET. Copyright © 2014 John Wiley & Sons, Ltd.     

Statistical and geostatistical investigations into the effects of the Gabcikovo hydropower plant on the groundwater resources of northwest Hungary / Analyses statistiques et géostatistiques des effets de la centrale hydroélectrique de Gabcikovo sur les ressources en eaux souterraines du Nord-Ouest de la Hongrie

Abstract

Abstract The construction of the Gabcikovo hydropower plant and the diversion of the Danube River over 25 km into an artificial channel in 1992 influenced the groundwater regime of the region considerably. Statistical and geostatistical methods are used to quantify changes of different groundwater characteristics on the Hungarian side of the river based on observations in the time period 1960–2000. External drift kriging was used to interpolate groundwater levels and the other related variables. While mean groundwater levels did not change appreciably, there are significant changes in the variability. Standard deviations of the groundwater levels and the amplitude of the annual cycle decreased near the old river bed of the Danube. The water-level fluctuations of the Danube have a decreased influence on the groundwater dynamics. Interrelationships between water levels in wells have also changed.     

Modelling the impacts of subsurface drainage on surface runoff and sediment yield in the Le Sueur Watershed,Minnesota, USA

Abstract

Tile drainage influences infiltration and surface runoff and is thus an important factor in the erosion process. Tile drainage reduces surface runoff, but questions abound on its influence on sediment transport through its dense network and into the stream network. The impact of subsurface tiling on upland erosion rates in the Le Sueur River watershed, USA, was assessed using the Water Erosion Prediction Project (WEPP) model. Six different scenarios of tile drainage with varying drainage coefficient and management type (no till and autumn mulch-till) were evaluated. The mean annual surface runoff depth, soil loss rate and sediment delivery ratio (SDR) for croplands, based on a 30-year simulation for the watershed with untiled autumn mulch-till (Scenario 1), were estimated to be 83.5 mm, 0.27 kg/m² and 86.7%, respectively; on no-till management systems (Scenario 4), the respective results were 72.3 mm, 0.06 kg/m² and 88.2%. Tile drains reduced surface runoff, soil loss and SDR estimates for Scenario 1 by, on average, 14.5, 8.1 and 7.9%, respectively; and for Scenario 4 by an estimated 31.5, 22.1 and 20.2%, respectively. The impact of tile drains on surface runoff, soil loss and SDR was greater under the no-till management system than under the autumn mulch-till management system. Comparison of WEPP outputs with those of the Soil Water Assessment Tool (SWAT) showed differences between the two methods.

Editor Z.W. Kundzewicz

Citation Maalim, F.K. and Melesse. A.M., 2013. Modelling impacts of subsurface drainage on surface runoff and sediment yield in the Le Sueur Watershed in Minnesota, USA. Hydrological Sciences Journal, 58 (3), 570–586.     

Analysis of flood propagation changes in the Kienstock—Bratislava reach of the Danube River/Analyse des changements de propagation des crues dans le tronçon Kienstock—Bratislava du Fleuve Danube

Abstract

In the first part of this study, a flood wave transformation analysis for the largest historical floods in the Danube River reach Kienstock–Bratislava was carried out. For the simulation of the historical (1899 and 1954) flood propagation, the nonlinear river model NLN-Danube (calibrated on the recent river reach conditions) was used. It was shown that the simulated peak discharges were not changed significantly when compared to their historical counterparts. However, the simulated hydrographs exhibit a significant acceleration of the flood wave movement at discharges of between 5000 and 9000 m³ s^-1. In the second part, the travel time-water level relationships between Kienstock and Bratislava were analysed on a dataset of the flood peak water levels for the period 1991–2002. An empirical regression routing scheme for the Danube short-term water level forecast at Bratislava station was derived. This is based on the measured water level at Kienstock gauging station.     

Capturing the essential spatial variability in distributed hydrological modelling: Infiltration parameters

Selecting the correct resolution in distributed hydrological modelling at the watershed scale is essential in reducing scale-related errors. The work presented herein uses information content (entropy) to identify the resolution which captures the essential variability, at the watershed scale, of the infiltration parameters in the Green and Ampt infiltration equation. A soil map of the Little Washita watershed in south-west Oklahoma, USA was used to investigate the effects of grid cell resolution on the distributed modelling of infiltration. Soil-derived parameters and infiltration exhibit decreased entropy as resolutions become coarser. This is reflected in a decrease in the maximum entropy value for the reclassified/derived parameters vis a vis the original data. Moreover, the entropy curve, when plotted against resolution, shows two distinct segments: a constant section where no entropy was lost with decreasing resolution and another part which is characterized by a sharp decrease in entropy after a critical resolution of 1209 m is reached. This methodology offers a technique for assessing the largest cell size that captures the spatial variability of infiltration parameters for a particular basin. A geographical information system (GIS) based rainfall-runoff model is used to simulate storm hydrographs using infiltration parameter maps at different resolutions as inputs. Model results up to the critical resolution are reproducible and errors are small. However, at resolutions beyond the critical resolution the results are erratic with large errors. A major finding of this study is that a large resolution (1209 m for this basin) yields reproducible model results. When modelling a river basin using a distributed model, the resolution (grid cell size) can drastically affect the model results and calibration. The error structure attributable to grid cell resolution using entropy as a spatial variability measure is shown.     

珠江河口经济动物体铜铅锌镉的含量

分别于2000年4月、2001年4月和2002年8月对珠江河口水域海洋经济动物体内Cu、Pb、Zn、Cd四种重金属元素的含量进行了调查分析,结果表明,14种经济动物体肌肉Cd、Cu、Pb、Zn各元素的平均含量分别是0.08、2.67、0.05、5.69mg·kg~(-1),其变化范围为nd～0.46mg·kg~(-1)、0.24～11.85mg·kg~(-1)、nd～0.26mg·kg~(-1)、1.55～18.36mg·kg~(-1)。甲壳类与头足类生物体内铜铅锌镉含量比较接近,远远高于鱼类的含量。所检测的14种经济类海洋动物中,虾姑、乌贼Cu的含量高于其余三种元素的含量,其余12种生物Zn的含量比另三种元素含量高。三次调查该水域经济类海洋动物体铜铅锌镉的含量基本一致。与水产品中有毒有害物质限量标准比较,14种被测样品铜、铅和镉的含量全部符合该标准的要求。     

TRANSFERABLE PHOSPHORUS IN SEDIMENTS OF THE HUANGHE RIVER ESTUARY ＇S ADJACENT WATERS

Based on a new idea for research on cycling of marine biogenic elements, this study showed that only the leachable form phosphorus in natural grain sizes manne sediments constitutes the transferable phosphorous in the sediments. The transferable phosphorus content in the natural grain sizes surface sediments in the Huanghe River estuary adjacent waters ranges from 58.5-69.8 μg/g, accounting for only 9.1%-11.0% of the total phosphorus content, whereas the leachable form (“transferable” )phosphorus content in the sediment after it was totally ground into powder was found to be 454.8-529.2μg/g, accounting for 73.4%-89.1% of the total phosphorus. Analysis of the correlation between thebill,ass of benthos and the leachable form (“transferable” ) phosphorus showed that most of the leachableform (“transferable”) phosphorus in the totally ground sediment did not participate in the marine biogeo chemical cycling. Furthermore, a synchronous survey on benthos showed that the biornass of meio-and maero-benthos exhibited good positive correlation with the leachable form of phosphorus in the naturalgrain sizes sediment, but peorer correlation with the leachable form (“transferable”) phosphorus in the totally ground sediment, indicating that transferable phosphorus in marine sediment is the leachable form of phosphorus in the natural grain sizes sediments, and is not the previously known leachable form(“transferable”) phosphorus obtained from the totally ground sediment.     

Measuring channel and gully cross-sections with an airborne laser altimeter

A laser altimeter, making 4000 measurements per second, was used to measure channel and gully morphology. The laser measurements provide quick, accurate and readily obtained data on the cross-section and morphology of channels and gullies in relation to the adjacent landscape. Although ground based techniques can be used to make these measurements, using a laser altimeter mounted in an aircraft allows data to be collected faster, with greater density and detail, and in areas with limited access for ground surveys. The laser altimeter data are valuable for measuring channel and gully cross-sections and roughness in relation to the surrounding landscape, for assessing soil loss from gullies and channels, and for providing input to the understanding of gully and channel dynamics in the landscape.     

The applicability of research on flood-drought tendency —an analysis on disastrous flood of Taihu Lake basin in June-July, 1991

In Taihu Lake basin during June–July in 1991, there happened a catastrophic flood, the precipitation reached that of 1954 and the water level was the highest in the history in Taihu Lake. This heavy flood, happening in the relatively humid period and being well accord with flood-drought change tendency, was early precautioned. The occurrence of the flood illustrated that using records of historical climate to predict flood-drough tendency is practically significant for hazard-reduction project.     

Spectrum characteristics of major ion concentrations at Wuhan sectoin of the Changjiang Rriver

Spectrum analyses of water quality time series have been carried out for five hydrometric stations including Wuhan hydrometric station of the Changjiang(Yangtze) River, etc. The fluctuations of Ca²⁺, Mg²⁺ and HCO ₃ ⁻ concentrations in river water under different physical geography conditions have about two-year cycle which is corresponding to hydrometeorological quasi-biannual-oscillation (QBO). Na⁺, Cl⁻ SO ₄ ²⁻ have about two-year cycle in the area lightly affected by human activities while two-year cycle doesn’t exist in the area heavily affected by human activities. All the fluctuations of major ions have about three-month cycle. The river diseharge fluctuation accounts for 43.9%, 45.1%, 54.3%, 33.9%, 30.3% and 42.7% of the variance of Ca²⁺, Mg²⁺, HCO ₃ ⁻ , Na⁺, Cl⁻, SO ₄ ²⁻ , respectively, at Wuhan from 1962 to 1985. According to the spectrum characteristic of major ions, the duration of the time series has to be at least 13 years for trend analysis of monthly water quality data. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 49671017). Biography: XIA Xing-hui(1971-), female, a native of Hunan Province, Ph. D. Her research interest includes environmental chemistry.