Research

4426 KiB

Open AccessArticle

Land Use/Cover Change Impacts on Water Table Change over 25 Years in a Desert-Oasis Transition Zone of the Heihe River Basin, China

by Jinfeng Wang, Yanchun Gao and Sheng Wang

Water 2016, 8(1), 11; https://0-doi-org.brum.beds.ac.uk/10.3390/w8010011 - 29 Dec 2015

Cited by 29 | Viewed by 6008

Abstract

Groundwater resources are becoming the primary factor for maintaining life in arid areas. Understanding land use/cover change and its effect on groundwater depth would enhance land use and groundwater management for typical desert-oasis transition zones. Reduction of groundwater recharge and increase of groundwater [...] Read more.

Groundwater resources are becoming the primary factor for maintaining life in arid areas. Understanding land use/cover change and its effect on groundwater depth would enhance land use and groundwater management for typical desert-oasis transition zones. Reduction of groundwater recharge and increase of groundwater exploitation during 1985 and 2010 led to the decrease of groundwater depth in Linze County. The region with groundwater depth less than 5 m decreased by 187 km² from 1985 to 2010 as a result of industrial growth, agricultural and economic development. Land use has undergone significant spatial and temporal changes. Farmland and built up land expanded by 53.02% and 30.91%, respectively. The expansion of farmland reached a peak between 1996 and 2005 with an increasing rate of 25.70%, while areas of grassland, woodland, water body and unused land decreased, and the decreasing rate was 9.38%, 58.35% and 19.81%. From 1985 to 2010, the groundwater depth rose slightly (0–1.2 m) in the edge of desert (24.21 km²), which was caused by the surrounding farmland irrigation recharge. The drawdown range of groundwater depth between 0 and 3 m was distributed in the central oasis, which was caused by the expansion of farmland and degradation of natural vegetation. This study aims to provide a basis for the reasonable utilization of water resources, the formation of management strategies, as well as to provide ecosystem stability and sustainable development of oases in the study area. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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6726 KiB

Open AccessArticle

Estimating Evapotranspiration from an Improved Two-Source Energy Balance Model Using ASTER Satellite Imagery

by Qifeng Zhuang and Bingfang Wu

Water 2015, 7(12), 6673-6688; https://0-doi-org.brum.beds.ac.uk/10.3390/w7126653 - 26 Nov 2015

Cited by 20 | Viewed by 6431 | Correction

Abstract

Reliably estimating the turbulent fluxes of latent and sensible heat at the Earth’s surface by remote sensing is important for research on the terrestrial hydrological cycle. This paper presents a practical approach for mapping surface energy fluxes using Advanced Spaceborne Thermal Emission and [...] Read more.

Reliably estimating the turbulent fluxes of latent and sensible heat at the Earth’s surface by remote sensing is important for research on the terrestrial hydrological cycle. This paper presents a practical approach for mapping surface energy fluxes using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images from an improved two-source energy balance (TSEB) model. The original TSEB approach may overestimate latent heat flux under vegetative stress conditions, as has also been reported in recent research. We replaced the Priestley-Taylor equation used in the original TSEB model with one that uses plant moisture and temperature constraints based on the PT-JPL model to obtain a more accurate canopy latent heat flux for model solving. The collected ASTER data and field observations employed in this study are over corn fields in arid regions of the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) area, China. The results were validated by measurements from eddy covariance (EC) systems, and the surface energy flux estimates of the improved TSEB model are similar to the ground truth. A comparison of the results from the original and improved TSEB models indicates that the improved method more accurately estimates the sensible and latent heat fluxes, generating more precise daily evapotranspiration (ET) estimate under vegetative stress conditions. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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936 KiB

Open AccessArticle

A Dynamic, Multivariate Sustainability Measure for Robust Analysis of Water Management under Climate and Demand Uncertainty in an Arid Environment

by Christian Hunter, Jorge Gironás, Diogo Bolster and Christos A. Karavitis

Water 2015, 7(11), 5928-5958; https://0-doi-org.brum.beds.ac.uk/10.3390/w7115928 - 30 Oct 2015

Cited by 13 | Viewed by 7467

Abstract

Considering water resource scarcity and uncertainty in climate and demand futures, decision-makers require techniques for sustainability analysis in resource management. Through unclear definitions of “sustainability”, however, traditional indices for resource evaluation propose options of limited flexibility by adopting static climate and demand scenarios, [...] Read more.

Considering water resource scarcity and uncertainty in climate and demand futures, decision-makers require techniques for sustainability analysis in resource management. Through unclear definitions of “sustainability”, however, traditional indices for resource evaluation propose options of limited flexibility by adopting static climate and demand scenarios, limiting analysis variables to a particular water-use group and time. This work proposes a robust, multivariate, dynamic sustainability evaluation technique and corresponding performance indicator called Measure of Sustainability (MoS) for resource management that is more adapted to withstand future parameter variation. The range of potential future climate and demand scenarios is simulated through a calibrated hydrological model of Copiapó, Chile, a case study example of an arid watershed under extreme natural and anthropogenic water stresses. Comparing MoS and cost rankings of proposed water management schemes, this paper determines that the traditional evaluation method not only underestimates future water deficits, but also espouses solutions without considering uncertainties in supply and demand. Given the uncertainty of the future and the dependence of resources upon climate and market trajectories, the MoS methodology proposes solutions that, while perhaps are not the most optimal, are robust to variations in future parameter values and are thus the best water management options in a stochastic natural world. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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3776 KiB

Open AccessArticle

Spatio-Temporal Patterns of Water Table and Vegetation Status of a Deserted Area

by Limin Duan, Tingxi Liu, Xixi Wang and Yanyun Luo

Water 2015, 7(10), 5788-5805; https://0-doi-org.brum.beds.ac.uk/10.3390/w7105788 - 23 Oct 2015

Cited by 6 | Viewed by 5927

Abstract

Understanding groundwater-vegetation interactions is crucial for sustaining fragile environments of desert areas such as the Horqin Sandy Land (HSL) in northern China. This study examined spatio-temporal variations in the water table and the associated vegetation status of a 9.71 km² area that [...] Read more.

Understanding groundwater-vegetation interactions is crucial for sustaining fragile environments of desert areas such as the Horqin Sandy Land (HSL) in northern China. This study examined spatio-temporal variations in the water table and the associated vegetation status of a 9.71 km² area that contains meadowland, sandy dunes, and intermediate transitional zones. The depth of the water table and hydrometeorologic parameters were monitored and Landsat Thematic Mapper (TM) and Moderate Resolution Imaging Spectroradiometer (MODIS) data were utilized to assess the vegetation cover. Spatio-temporal variations over the six-year study period were examined and descriptive groundwater–vegetation associations developed by overlaying a water table depth map onto a vegetation index map derived from MODIS. The results indicate that the water table depends on the local topography, localized geological settings, and human activities such as reclamation, with fluctuations occurring at annual and monthly scales as a function of precipitation and potential evapotranspiration. Locations where the water table is closer to the surface tend to have more dense and productive vegetation. The water table depth is more closely associated with vegetative density in meadowlands than in transitional zones, and only poorly associated with vegetation in sandy dunes. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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2941 KiB

Open AccessArticle

Flow Regime Classification and Hydrological Characterization: A Case Study of Ethiopian Rivers

by Belete Berhanu, Yilma Seleshi, Solomon S. Demisse and Assefa M. Melesse

Water 2015, 7(6), 3149-3165; https://0-doi-org.brum.beds.ac.uk/10.3390/w7063149 - 22 Jun 2015

Cited by 43 | Viewed by 11295

Abstract

The spatiotemporal variability of a stream flow due to the complex interaction of catchment attributes and rainfall induce complexity in hydrology. Researchers have been trying to address this complexity with a number of approaches; river flow regime is one of them. The flow [...] Read more.

The spatiotemporal variability of a stream flow due to the complex interaction of catchment attributes and rainfall induce complexity in hydrology. Researchers have been trying to address this complexity with a number of approaches; river flow regime is one of them. The flow regime can be quantified by means of hydrological indices characterizing five components: magnitude, frequency, duration, timing, and rate of change of flow. Similarly, this study aimed to understand the flow variability of Ethiopian Rivers using the observed daily flow data from 208 gauging stations in the country. With this process, the Hierarchical Ward Clustering method was implemented to group the streams into three flow regimes (1) ephemeral, (2) intermittent, and (3) perennial. Principal component analysis (PCA) is also applied as the second multivariate analysis tool to identify dominant hydrological indices that cause the variability in the streams. The mean flow per unit catchment area (QmAR) and Base flow index (BFI) show an incremental trend with ephemeral, intermittent and perennial streams. Whereas the number of mean zero flow days ratio (ZFI) and coefficient of variation (CV) show a decreasing trend with ephemeral to perennial flow regimes. Finally, the streams in the three flow regimes were characterized with the mean and standard deviation of the hydrological variables and the shape, slope, and scale of the flow duration curve. Results of this study are the basis for further understanding of the ecohydrological processes of the river basins in Ethiopia. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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1517 KiB

Open AccessArticle

Spatiotemporal Analysis of Extreme Hourly Precipitation Patterns in Hainan Island, South China

by Wenjie Chen, Chenghao Chen, Longbing Li, Litao Xing, Guoru Huang and Chuanhao Wu

Water 2015, 7(5), 2239-2253; https://0-doi-org.brum.beds.ac.uk/10.3390/w7052239 - 13 May 2015

Cited by 16 | Viewed by 6259

Abstract

To analyze extreme precipitation patterns in Hainan Island, hourly precipitation datasets from 18 stations, for the period from 1967 to 2012, were investigated. Two precipitation concentration indices (PCI) and 11 extreme precipitation indices (EPI) were chosen. PCI1 indicated a moderate seasonality in yearly [...] Read more.

To analyze extreme precipitation patterns in Hainan Island, hourly precipitation datasets from 18 stations, for the period from 1967 to 2012, were investigated. Two precipitation concentration indices (PCI) and 11 extreme precipitation indices (EPI) were chosen. PCI1 indicated a moderate seasonality in yearly precipitation and PCI2 showed that at least 80% of the total precipitation fell in 20% of the rainiest hours. Furthermore, the spatial variations of PCI1 and PCI2 differed. Linear regression indicated increasing trends in 11 of the calculated EPI. Principal component analysis found that the first recalculated principal component represented the 11 EPI. The recalculated principal component revealed an increasing trend in precipitation extremes for the whole island (except the interior section). Trend stability analysis of several of EPI suggested that the southern parts of Hainan Island, and especially the city of Sanya, should receive more attention to establish the drainage facilities necessary to prevent waterlogging. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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Review

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290 KiB

Open AccessReview

Vapor Flow Resistance of Dry Soil Layer to Soil Water Evaporation in Arid Environment: An Overview

by Xixi Wang

Water 2015, 7(8), 4552-4574; https://0-doi-org.brum.beds.ac.uk/10.3390/w7084552 - 21 Aug 2015

Cited by 34 | Viewed by 6859

Abstract

Evaporation from bare sandy soils is the core component of the hydrologic cycle in arid environments, where vertical water movement dominates. Although extensive measurement and modeling studies have been conducted and reported in existing literature, the physics of dry soil and its function [...] Read more.

Evaporation from bare sandy soils is the core component of the hydrologic cycle in arid environments, where vertical water movement dominates. Although extensive measurement and modeling studies have been conducted and reported in existing literature, the physics of dry soil and its function in evaporation is still a challenging topic with significant remaining issues. Thus, an overview of the previous findings will be very beneficial for identifying further research needs that aim to advance our understanding of the vapor flow resistance (VFR) effect on soil water evaporation as influenced by characteristics of the dry soil layer (DSL) and evaporation zone (EZ). In this regard, six measurement and four modeling studies were overviewed. The results of these overviewed studies, along with the others, affirm the conceptual dynamics of DSL and EZ during drying or wetting processes (but not both) within dry sandy soils. The VFR effect tends to linearly increase with DSL thickness (δ) when δ < 5 cm and is likely to increase as a logarithmic function of δ when δ ≥ 5 cm. The vaporization-condensation-movement (VCM) dynamics in a DSL depend on soil textures: sandy soils can form a thick (10 to 20 cm) DSL while sandy clay soils may or may not have a clear DSL; regardless, a DSL can function as a transient EZ, a vapor condensation zone, and/or a vapor transport medium. Based on the overview, further studies will need to generate long-term continuous field data, develop hydraulic functions for very dry soils, and establish an approach to quantify the dynamics and VFR effects of DSLs during wetting-drying cycles as well as take into account such effects when using conventional (e.g., Penman-Monteith) evaporation models. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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Other

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2490 KiB

Open AccessCase Report

Flood-Runoff in Semi-Arid and Sub-Humid Regions, a Case Study: A Simulation of Jianghe Watershed in Northern China

by Hua Jin, Rui Liang, Yu Wang and Prasad Tumula

Water 2015, 7(9), 5155-5172; https://0-doi-org.brum.beds.ac.uk/10.3390/w7095155 - 22 Sep 2015

Cited by 41 | Viewed by 6554

Abstract

This paper presents a modeling application of surface runoff using the Hydrologic Modelling System (HEC-HMS). A case study was carried out for the Jianghe watershed, a typical semi-arid and sub-humid geo-climatic region in northern China. Two modeling schemes using different descriptive sub-mechanism models [...] Read more.

This paper presents a modeling application of surface runoff using the Hydrologic Modelling System (HEC-HMS). A case study was carried out for the Jianghe watershed, a typical semi-arid and sub-humid geo-climatic region in northern China. Two modeling schemes using different descriptive sub-mechanism models provided by HEC-HMS for runoff volume, direct runoff and routing (channel flow) were investigated. The modeling results were compared with historical observation data. This work shows that HEC-HMS can be a suitable modeling tool for specific situations in China. With the appropriate selection of the sub-mechanism models, HEC-HMS can be applied to various situations, including the typical semi-arid and sub-humid conditions in northern China. Full article

(This article belongs to the Special Issue Hydrologic System Analysis, Patterns, and Predictions for Arid and Semi-arid Environment)

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