Research advances in eco-hydrological process and function

Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling relationship, and also summarizes research and presents a method of combining isotopic technology with hydro-chemical methods, for the study of eco-hydrological process and function in different landscape zones. We then examine research trends for future direction and development of this field.

A review on eco-hydrological effects of condensation water

Almost half the world is suffering from drought at different levels. Since arid and semi-arid regions are characterized by extreme shortage and precipitation uncertainty, water availability is the most impo~.nt limiting factor in arid lands, and any additional source of moisture, such as condensation water, may have a positive impact upon the ecosystem. Therefore, extensive research has been carried out on condensation. Based on articles and relevant documents on the subject, this paper reviews systemati- cally and comprehensively the latest research achievements in several main aspects, including eco-hydrological effects of condensation water on plants, small animals, microbiotic crusts, soil moisture balance, ground water recharge and anthropo- genic utilization. History and trends of research about eco-hydrological effects of condensation water are intensively analyzed in order to summarize existing problems and offer opinions and suggestions for future study.

Review of several problems on the study of eco-hydrological processes in arid zones

Ecosystem degradation is a common and cardinal environmental problem in arid zones. The change in the eco-hydrological processes is the basic cause responsible for such a problem. The study on the eco-hydrological processes in arid zones has become a forefront and focus of the eco-environmental research. Recent studies on eco-hydrological processes in arid zones show that the primary vegetation pattern and its eco-hydrological effect are of the most stable state of the ecosystem in arid zones. Special water absorption ways of plants in arid zones and the hydraulic lift and reverse hydraulic lift functions of some plants are the key mechanisms to maintain the stability of the ecosystem in arid zones. In the case of water shortage, ensuring ecological water requirement and maintaining proper ecological ground- water table are the prerequisite to keep healthful operation of the ecosystem in arid zones. The paper reviews some advances in the study of eco-hydrological processes in arid zones. It puts

Prospects of eco-hydrological model for sponge city construction

Introduction:Understanding complex urban eco-hydrological processes through models is an important approach in sponge city construction.However,the research on this has not kept pace with the urgent need for sustainable development of urban water resources,which makes the current construction efficiencies unsatisfactory.Outcomes:This review highlights the importance of establishing a multi-scale urban distributed eco-hydrological model by analyzing the connotations of sponge city construction.Hydrological models that can be configured for sponge city construction were selected.Traditional models have limitations in coupling ecological and hydrological processes,multi-scale and landscape-based simulations,refined simulations,and computational efficiency.By contrast,cellular automaton has a discrete data structure in space,time,and states,is capable of bottom-up computing,and provides a new conceptual framework for simulating complex urban eco-hydrological processes.Discussion and Conclusion:Future model development may focus on the conduction of multi-scale simulation systems,the simulation of coupled urban eco-hydrological processes,the quantification of eco-hydrological responses to land cover composition,spatial configuration and low impact development practices,and improving simulation accuracy.

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.

Bibliometrics-based Research Hotspots and Development Trends in Eco-hydrology of Dammed Rivers

Water conservation initiatives satisfy the demand for water supply,electricity generation,irrigation,and flood control.While helping humanity,they have also altered the ecosystem of natural rivers,impacted river ecology,disrupted river continuity,and jeopardized the existence of aquatic creatures in rivers.Studying the impacts of dam construction on rivers can enhance our knowledge of river ecological and environmental concerns and help sustain the health of river ecosystems,thereby realizing the harmony between humans and water in both theoretical and practical aspects.This study used bibliometrics and constructed an author-keyword 2-mode matrix network using Co-Occurrence software to identify the hotspots and research trend in eco-hydrology of dammed rivers.We identified‘FLOW’‘SEDIMENT’‘QUALITY’and‘MODEL’as the research hotspots in the ecological impact of dammed rivers,and combined the related literatures,we highlight the research progress in the four directions.Then the research shortcomings and prospect were discussed,including strengthening the monitoring and analysis of critical ecological variables,enhancing the hydrological monitoring density for small rivers,strengthening the research of relationship between eutrophication and zooplankton,establishing multiscale approaches,and combining multi-sources information technologies to improve parameter accuracy in the model research.

An Eco-Hydrology Wireless Sensor Demonstration Network in High-Altitude and Alpine Environment in the Heihe River Basin of China

The emerging of Wireless Sensor Network (WSN) technology has brought new opportunities for data intensive observation in eco-hydrological research and environment monitoring. To make up for the insufficiencies of space observation data for models in eco-hydrology processes research of inland river basin which constrain the construction of accurate modeling and simulation, a sub-basin of the Heihe River Basin named Hulugou has been selected to perform the deployment and research for wireless sensor network from the perspective of eco-hydrology. In this paper, we discussed the system framework, the demonstration research area, the deployment of sensor nodes and the network topology of wireless sensor network. Finally, the study has summarized existing problems and experiences of wireless sensor network in these eco-hydrological applications and the available researches in hard environment. In the future, we will deploy a large number of sensor nodes in the long-term fine-grained eco-hydrological elements observing environment to form lots of homogeneous or heterogeneous wireless sensor networks.

Ecological water demand of natural vegetation in the lower Tarim River

We have appraised the relationships between soil moisture, groundwater depth, and plant species diversity in the lower reaches of the Tarim River in western China, by analyzing field data from 25 monitoring wells across eight study sites and 25 permanent vegetation survey plots. It is noted that groundwater depth, soil moisture and plant species diversity are closely related. It has been proven that the critical phreatic water depth is five meters in the lower reaches of the Tarim River. We acquired the mean phreatic evaporation of different groundwater levels every month by averaging the two results of phreatic evaporation using the Qunk and Averyanov formulas. Based on different vegetation types and acreage with different groundwater depth, the total ecological water demand （EWD） of natural vegetation in 2005 was 2.4×10^8 m^3 in the lower reaches of the Tarim River. Analyzing the monthly EWD, we found that the EWD in the growth season （from April to September） is 81% of the year＇s total EWD. The EWD in May, June and July was 47% of the year＇s total EWD, which indicates the best time for dispensing artificial water. This research aims at realizing the sustainable development of water resources and provides a scientific basis for water resource management and sound collocation of the Tarim River Basin.

Hydrological setting of infertile species-rich wetland——a case study in the warm temperate Japan

The detailed groundwater flow and water chemistry to illustrate landscape structure of the infertile peatless mire by using piezometers and groundwater wells were measured. The instruments were installed in lines through a small spring-fed wetland underlying little peat from the hillslope to the valley bottom in southwestern Japan. Flow net and EC data clearly indicated that the wetland was situated in a high-EC groundwater upspring area. The low-productivity graminous vegetation was related with four hydrological factors such as: (1) high water level; (2) low-EC(<25 micro S/cm) groundwater; (3) weakly upward hydraulic gradient; and (4) overflowing of negatively pressured groundwater. In other words, the “old or deep groundwater” constructed the foundation of slope-wetland, and maintained the high groundwater level. In contrast, overflowing “youthful groundwater” is supplied from head of slope-wetland preferentially through the shallow substratum. The plant communities of the peatless mire in southwestern Japan are similar to those of raised bog in northern cool temperate Japan. There have been some reports verifying that the underlying mineral substrata of such wetlands were quartzile rocks such as granite, rhyolite, chart and well-leached sand. Results showed (1) low cation availability affects the water acidity; (2) upward seepage of high-EC groundwater composed the foundation of the investigated peatless mire; and (3) the poor mineral condition seems to play a similar role to northern ombrotrophic(rain-fed) condition.

Turkey Creek—A Case Study of Ecohydrology and Integrated Watershed Management in the Low-Gradient Atlantic Coastal Plain, USA

Water yield, water supply and quality, wildlife habitat, and ecosystem productivity and services are important societal concerns for natural resource management in the 21st century. Watershed-scale ecohydrologic studies can provide needed context for addressing complex spatial and temporal dynamics of these functions and services. This study was conducted on the 5240 ha Turkey Creek watershed (WS 78) draining a 3rd order stream on the Santee Experimental Forest within the South Carolina Atlantic Coastal Plain, USA. The study objectives were to present the hydrologic characteristics of this relatively undisturbed, except by a hurricane (Hugo, 1989), forested water-shed and to discuss key elements for watershed management, including water resource assessment (WRM), modeling integrated water resources management, environmental assessment, land use planning, social impact assessment, and information management. Runoff coefficients, flow duration curves, flood and low flow frequency curves, surface and ground water yields were assessed as elements of the WRM. Results from the last 10 years of interdisciplinary studies have also advanced the understanding of coastal ecohydrologic characteristics and processes, water balance, and their modeling including the need of high resolution LiDAR data. For example, surface water dynamics were shown to be regulated primarily by the water table, dependent upon pre- cipitation and evapotranspiration (ET). Analysis of pre- and post-Hugo streamflow data showed somewhat lower but insignificant (α = 0.05) mean annual flow but increased frequency of larger flows for the post-Hugo compared with the pre-Hugo level. However, there was no significant difference in mean annual ET, potentially indicating the resiliency of this coastal forest. Although the information from this study may be useful for comparison of coastal ecohydrologic issues, it is becoming increasingly clear that multi-site studies may be warranted to understand these complex systems in the face of climate change, sea level rise, and increasing development in coastal regions.

Analysis of vegetation response to rainfall with satellite images in Dongting Lake

We analyzed the Normalized Difference Vegetation Index （NDVI） from satellite images and precipitation data from meteorological stations from 1998 to 2007 in the Dongting Lake wetland watershed to better understand the eco-hydrological effect of atmospheric precipitation and its relationship with vegetation. First,we analyzed its general spatio-temporal distribution using its mean,standard deviation and linear trend. Then,we used the Empirical Orthogonal Functions （EOF） method to decompose the NDVI and precipitation data into spatial and temporal modes. We selected four leading modes based on North and Scree test rules and analyzed the synchronous seasonal and inter-annual variability between the vegetation index and precipitation,distinguishing time-lagged correlations between EOF modes with the correlative degree analysis method. According to our detailed analyses,the vegetation index and precipitation exhibit a prominent correlation in spatial distribution and seasonal variation. At the 90% confidence level,the time lag is around 110 to 140 days,which matches well with the seasonal variation.

Hysteresis in sap flow and its controlling mechanisms for a deciduous broad-leaved tree species in a humid karst region

The critical zone(CZ) represents the intersection of the biosphere with the atmosphere, hydrosphere and lithosphere.Understanding the hydrological processes and human impact factors on the CZ is fundamental to sustainable water resources management for agroforestry. Transpiration(T) is an important component of terrestrial evapotranspiration(ET), and understanding the time lag(TL) between vegetation transpiration and meteorological factors can improve our knowledge of the mechanisms of vegetation adaptability to a changing environment. However, the controlling factors on the TL remain poorly understood. Therefore, the objective of this study is identifying the temporal dynamics of key controlling factors on the TL, using a typical deciduous broad-leaved tree species(Zenia insigins Chun) of CZ in subtropical humid karst regions. This species is used as an example to explore the characteristics of the TL between SF(sap flow) and hydro-meteorological forcing. Sap flow in these 6 trees was monitored using the thermal dissipation probes(TDP). Results showed that:(1) the peak of diurnal sap flow generally lagged behind PAR but preceded Ta(air temperature), RH(relative humidity) and VPD(vapor pressure deficit), with the mean TL of-67.4 min(PAR), 90.5 min(Ta), 91.6 min(RH) and 92.9 min(VPD), respectively;(2) TL had no significant relationships with the daily mean meteorological factors and soil moisture, but was highly(R^2>0.66) correlated to CRs(changing rates of meteorological factors) in the morning;(3) At seasonal scale, the sap flow rate and TL both were controlled by the seasonality of precipitation and temperature. Overall, the seasonality of the TL was caused by plants' high water loss and strongly active physiological response in hot seasons, leading to close stomata earlier than in cold seasons;(4) The reason why CRs proposed can explain the TL better than mean values of metrological factors is that the CRs considered the distribution and change processes of metrological factors in the daytime. This study may be helpful for understanding the physiological response of vegetation to climatic change, and may be useful for constructing models to simulate transpiration processes more accurately during a day.