Eco-hydrological Characteristics Research Articles

Multipurpose Plans for the Sustainability of the Greek Lakes: Emphasis on Multiple Stressors

Lake Ecosystems have experienced a significant loss of their ecological value due to various human activities. It has been recognized that the continued alteration of freshwater biodiversity is not sustainable, and also, it has been realized that less modified freshwater ecosystems provide significant economic and social benefits to society. In Greece, changes in land and water management, driven by the increase in agricultural production and the urban expansion, have created multiple stressors on lentic ecosystems which cannot be ignored any longer. The objective of the present study is to describe some of these stressors, and to identify their impacts on Greek lakes. We collected an extensive dataset from twelve natural lakes using several metrics, also suggested by the Water Framework Directive (WFD), along with specific ecohydrological characteristics. Our results demonstrate severe impact on water quality and quantity with consequence to the lake’s functions, and extended eutrophication in almost all lakes. The Greek lakes have been subjected to various hydromorphological alterations, which affect their metabolism, while the aforementioned effects are further maximized due to particularities of the Mediterranean climate. The set up of good management practices through multipurpose management plans are also discussed.

Impact of the Sanmenxia and Xiaolangdi Reservoirs Operation on the Hydrologic Regime of the Lower Yellow River

AbstractTo evaluate the alteration of the hydrologic regime in the lower Yellow River caused by the different operational modes of the Sanmenxia and Xiaolangdi Reservoirs, daily stream flow data obtained from the Huayuankou Hydrological Station between 1949 and 2010 were analyzed. The hydrologic regimes before and after different reservoir operations were quantitatively analyzed using the range of variability approach (RVA) based on the indicators of hydrologic alteration (IHA). The results showed that the hydrologic regime of the lower Yellow River changed significantly after the reservoirs began operation, In addition, there was a significant difference in ecohydrological characteristics between operation modes. This research further explains the hydrologic regime of the river. It can be used for future water resources management and ecological scheduling within the lower Yellow River Basin.

Transpiration in an oil palm landscape: effects of palm age

Abstract. Oil palm (Elaeis guineensis Jacq.) plantations cover large and continuously increasing areas of humid tropical lowlands. Landscapes dominated by oil palms usually consist of a mosaic of mono-cultural, homogeneous stands of varying age, which may be heterogeneous in their water use characteristics. However, studies on the water use characteristics of oil palms are still at an early stage and there is a lack of knowledge on how oil palm expansion will affect the major components of the hydrological cycle. To provide first insights into hydrological landscape-level consequences of oil palm cultivation, we derived transpiration rates of oil palms in stands of varying age, estimated the contribution of palm transpiration to evapotranspiration, and analyzed the influence of fluctuations in environmental variables on oil palm water use. We studied 15 two- to 25-year old stands in the lowlands of Jambi, Indonesia. A sap flux technique with an oil palm specific calibration and sampling scheme was used to derive leaf-, palm- and stand-level water use rates in all stands under comparable environmental conditions. Additionally, in a two- and a 12-year old stand, eddy covariance measurements were conducted to derive evapotranspiration rates. Water use rates per leaf and palm increased 5-fold from an age of 2 years to a stand age of approx. 10 years and then remained relatively constant. A similar trend was visible, but less pronounced, for estimated stand transpiration rates of oil palms; they varied 12-fold, from 0.2 mm day−1 in a 2-year old to 2.5 mm day−1 in a 12-year old stand, showing particularly high variability in transpiration rates among medium-aged stands. Comparing sap flux and eddy-covariance derived water fluxes suggests that transpiration contributed 8 % to evapotranspiration in the 2-year old stand and 53 % in the 12-year old stand, indicating variable and substantial additional sources of evaporation, e.g., from the soil, the ground vegetation and from trunk epiphytes. Diurnally, oil palm transpiration rates were characterized by an early peak between 10 and 11 a.m.; there was a pronounced hysteresis in the leaf water use response to changes in vapor pressure deficit for all palms of advanced age. On the day-to-day basis this resulted in a relatively low variability of oil palm water use regardless of fluctuations in vapor pressure deficit and radiation. We conclude that oil palm dominated landscapes show some spatial variations in (evapo)transpiration rates, e.g., due to varying age-structures, but that the temporal variability of oil palm transpiration is rather low. The stand transpiration of some of the studied oil palm stands was as high or even higher than values reported for different tropical forests, indicating a high water use of oil palms under yet to be explained site or management conditions. Our study provides first insights into the eco-hydrological characteristics of oil palms as well as a first estimate of oil palm water use across a gradient of plantation age. It sheds first light on some of the hydrological consequences of the continuing expansion of oil palm plantations.

A case study of regional eco-hydrological characteristics in the Tao River Basin, northwestern China, based on evapotranspiration estimated by a coupled Budyko Equation-crop coefficient approach

In a case study in Tao River Basin, China, we derived a high spatial-resolution regional distribution of evapotranspiration (ET) using the single crop coefficient method and Budyko equation. We then further analyzed the spatio-temporal characteristics of this diverse eco-hydrological basin from 2001–2010. The results suggest that the single crop coefficient method based on leaf area index captures better spatial and temporal dynamics of the regional ET than did the Budyko Equation method. The rising temperature was the main reason for the increasing ET in the Tao River Basin during 2001–2010. Areas with high ET efficiency were distributed mainly in the areas where the vegetation coverage was high, and a lower runoff coefficient responded. The estimated spatial patterns of ET allowed an improved understanding of the eco-hydrological processes within the Tao River Basin and the method used might be generalized as a reference for future regional-scale eco-hydrological research.

Bacterial structures and ecosystem functions in glaciated floodplains: contemporary states and potential future shifts

Glaciated alpine floodplains are responding quickly to climate change through shrinking ice masses. Given the expected future changes in their physicochemical environment, we anticipated variable shifts in structure and ecosystem functioning of hyporheic microbial communities in proglacial alpine streams, depending on present community characteristics and landscape structures. We examined microbial structure and functioning during different hydrologic periods in glacial (kryal) streams and, as contrasting systems, groundwater-fed (krenal) streams. Three catchments were chosen to cover an array of landscape features, including interconnected lakes, differences in local geology and degree of deglaciation. Community structure was assessed by automated ribosomal intergenic spacer analysis and microbial function by potential enzyme activities. We found each catchment to contain a distinct bacterial community structure and different degrees of separation in structure and functioning that were linked to the physicochemical properties of the waters within each catchment. Bacterial communities showed high functional plasticity, although achieved by different strategies in each system. Typical kryal communities showed a strong linkage of structure and function that indicated a major prevalence of specialists, whereas krenal sediments were dominated by generalists. With the rapid retreat of glaciers and therefore altered ecohydrological characteristics, lotic microbial structure and functioning are likely to change substantially in proglacial floodplains in the future. The trajectory of these changes will vary depending on contemporary bacterial community characteristics and landscape structures that ultimately determine the sustainability of ecosystem functioning.

Hydrological Variation Characteristics of Rivers in Humid Region: Oujiang River, China

Oujiang River was selected as the case study, and a dataset of daily flow series at Xuren Station was used to explore the hydrologic characteristics of rivers in humid areas, by using the ‘Indicators of Hydrologic Alteration’ approach and ‘Range of Variability Approach’. Results showed that the overall alteration of the hydrological regime for Oujiang River belonged to the low alteration category, and some key eco-hydrological characteristics should be protected in certain key periods to maintain the integrality and health status of river ecosystems.

Estimating the regional evapotranspiration in Zhalong wetland with the Two-Source Energy Balance (TSEB) model and Landsat7/ETM+ images

This paper aims to integrate a numerical model, vegetation index, and regional evapotranspiration estimation to assess the water cycle in Zhalong wetland, China with the aid of remote sensing technologies. An interdisciplinary analysis was performed to study the eco-hydrological characteristics of the wetland ecosystem. In particular, a new solution for solving the Two-Source Energy Balance (TSEB) was developed and applied. This new solution method is based on a definition of the aerodynamic temperature in a two-layer ground surface structure. Following this new solution for TSEB, the outputs of the Surface Energy Balance Algorithm (SEBAL) may be used as the inputs for TSEB to avoid the complex calculations of the bulk boundary layer and soil surface resistance. The new solution method makes the implementation of TSEB much easier when bi-directional thermal infrared remote sensing images are not available. Daily evapotranspiration and vegetation index of the wetland were calculated from six scenes of Landsat7/ETM+ remote sensing images acquired during 2001 and 2002 in our case study. Spatial distribution of daily evapotranspiration was also provided to help realize the wetland condition. The seasonal changes of vegetation index and evapotranspiration for some typical wetland ground surfaces were analyzed and presented as well to explore the multitemporal variations of plant species holistically. Ultimately, such integrative analysis aids in understanding the general biological patterns associated with these wetland vegetation cover, while specific situations of the wetland ecosystem can be recognized.

Soil Water Repellency: A Method of Soil Moisture Sequestration in Pinyon–Juniper Woodland

Encroachment of pinyon–juniper woodland into rangeland ecosystems is prevalent across the western United States. Mechanisms associated with this successful encroachment are speculative, but probably, in part, involve the effective use of water resources. We explored the ecohydrological characteristics of a two‐needle pinyon pine (Pinus edulisEngelm.)–Utah juniper [Juniperus osteosperma(Torr.) Little] woodland on the Colorado Plateau in Utah. We have discovered that a high level of natural soil water repellency or hydrophobicity exists under the canopies of both pinyon and juniper species. We found, following summer precipitation events, that soil water repellency under trees concentrated the soil water below the surface through finger flow or bypass infiltration, contrasting with piston flow and much more uniform soil wetting in intercanopy locations. We propose that the trees “engineer” their environment, creating water repellency as a way of providing an ecohydrological advantage and reducing potential water uptake by shallow‐rooted herbaceous species. In addition, we speculate that soil water repellency may be a major contributing factor to the “nutrient islands” observed to persist under juniper canopies even after the trees have been cut down and removed.

Study on the spatiotemporal variability of eco-hydrological characteristics of the rivers in the Longitudinal Range-Gorge Region and their driving forces

Taking two typical rivers in high mountains and steep gorge areas as example, this paper analyzes the spatiotemporal variability of the eco-hydrological characteristics and the driving forces leading to changes. Firstly, based on the species-environmental data processing, this paper adopts canonical correspondence analysis (CCA) method to identify the environmental factors influencing the distribution of river bank vegetation. Secondly, this study uses the ecological diversity index to represent the spatiotemporal variability of ecological characteristics. Thirdly, this paper uses the multiple correlation method to analyze the relationship between the hydrological factors and meteorological factors, and to identify the key factors leading to the hydrological regime changes. At last, based on the analysis of basin water quality data, this paper analyzes the regularity of spatiotemporal variability and its driving forces. By the systematic analysis on the outcome, we could get that the spatiotemporal distribution of eco-hydrological characteristics shows the regular changes from the upstream to downstream (from the north to the south), and the spatiotemporal variability of eco-hydrological characteristics is typical from the east to the west. Altitude, aspect and water distribution are the primary natural driving forces leading to the spatiotemporal variability of eco-hydrological characteristics; and exploitation and operation of hydroelectric power station, construction of road on the river bank, and basin land utilization are the main human driving forces.

Landscape pattern and eco-hydrological characteristics at the upstream of Minjiang River, China

Based on three scenes of Landsat 5 Thematic Mapper (TM) satellite images acquired on June 26, 1994, 12 land cover types were identified by the supervised classification techniques. The precipitation, runoff, and normalized difference vegetation index (NDVI) data of six catchments were accumulated from April to September in 1992, 1993, and 1995. A new eco-hydrological index, expressed by the difference between precipitation and runoff divided by the product of precipitation and NDVI, was used in this study to represent the eco-hydrological functions of different catchments. The results were: (1) The selected six catchments at the upstream of Minjiang River, China were different in landscape patterns in terms of landscape type and cover. There were higher contagion, lower edge density and diversity index in the Shouxi catchments and lower contagion, higher edge density and diversity index in the Zagunao catchments. (2) Eco-hydrological indexes had remarkable differences among different catchments. The highest eco-hydrological index was found in the Shouxi catchments, which indicated higher precipitation holding capacity of vegetation therein. While the lower eco-hydrological index was found in the Zagunao catchments, which indicated its lower precipitation holding capacity of vegetation. (3) High correlation was detected between the landscape indexes and eco-hydrological indexes. Eco-hydrological index was positively correlated with landscape contagion in contrast with the negative correlation with landscape diversity and edge density.

Ecological characteristics of soil water and its relations to landform and vegetation in a small semiarid watershed in a loess hilly area of China

There is an urgent need to study soil water resources and eco-hydrological characteristics in depth so as to carry forward ecological environmental construction in the Loess Plateau. Soil moisture was measured to a depth of 5 m on 11 sites with different landforms and land uses in a transect of the Zhonglianchuan watershed during 2002. The watershed is located in the northern Yuzhong County, Gansu Province, and is part of a semiarid and loess hilly area. There were different types of soil moisture variations in 2002 on the 11 sites. Soil moisture contents were low on all sites, and the average water contents at 2 to 5-m depth were usually lower than 10% by weight, and the lowest water contents were found in slope land under Medicago sativa and Caragana korshinskii vegetation. The dry soil layer is common in this area, not only under planted vegetation but also under natural vegetation. The soil moisture in a slope segment or area can be increased by collecting and harvesting surface runoff from upslope areas. One effective way to collect runoff is by constructing level terraces, alternating with sloping lands. The proportion of various grasslands, acreage of alfalfa, and sustainable development of the region should be further studied in order to successfully convert cultivated land into grassland.

TOWARDS ACHIEVING FUNCTIONAL ECOSYSTEM MIMICRY WITH RESPECT TO WATER CYCLING IN SOUTHERN AUSTRALIAN AGRICULTURE

The southern Australian landscape is characterised by large climatic variability and an old, weathered surface with generally low hydraulic gradients. Many of these landscapes are prone to salinisation. The original ecosystems have strategies to cope with this environment in ways which minimise runoff and groundwater recharge. Replacement of these ecosystems with conventional agriculture has resulted in large-scale disruption of the natural water cycle with severe environmental, economic and social consequences. Sustainable agricultural systems aimed at mimicking natural hydrology must either minimise groundwater recharge over most of this landscape or intercept groundwater discharge in lower parts of the landscape prior to salinisation to restore the original hydrological balance. Empirical and theoretical analyses suggest that however vegetation is managed in the landscape, effective water balance control will be achieved only at a leaf area index approaching that of the natural state, indicating revegetation of most or all parts of the catchment with either trees or plants with similar ecohydrological characteristics as trees. There are at present few economically- attractive agricultural systems able to achieve hydrologic mimicry likely to be adopted at the necessary scale.

The Development of Peat Lands

great scientific as well as practical interest. Reclamation of such land, and use of the peat itself, is a matter of importance throughout northern Europe, and for this reason, if no other, it is highly desirable to know something of the processes involved in peat accumulation, and of the factors controlling it. Since the study of peat lands entails dealing with a mass of complex relations between organisms and their environments, our understanding of them is necessarily fragmentary and far from complete. Nevertheless, if a brief outline is presented of one type of vegetation and soil sequence which occurs in many parts of northern Britain, the scene may be set for a consideration of the way in which variations in the major environmental factors-climate, geology, relief, and organisms-can modify this type of succession over long periods of time, in different parts of the world. First, however, it