Water Flow Regulation Research Articles

New paradigm for saving the world’s forests?

Book review: Douglas, J. and Simula, M. 2010. The Future of the World’s Forests. Ideas vs Ideologies. World Forests, volume 7. Springer. 211p.

The use of remote sensing to quantify wetland loss in the Choke Mountain range, Upper Blue Nile basin, Ethiopia

Abstract. Wetlands provide multiple ecosystem services such as storing and regulating water flows and water quality, providing unique habitats to flora and fauna, and regulating micro-climatic conditions. Conversion of wetlands for agricultural use is a widespread practice in Ethiopia, particularly in the southwestern part where wetlands cover large areas. Although there are many studies on land cover and land use changes in this region, comprehensive studies on wetlands are still missing. Hence, extent and rate of wetland loss at regional scales is unknown. The objective of this paper is to quantify wetland dynamics and estimate wetland loss in the Choke Mountain range (area covering 17 443 km2) in the Upper Blue Nile basin, a key headwater region of the river Nile. Therefore, satellite remote sensing imagery of the period 1986–2005 were considered. To create images of surface reflectance that are radiometrically consistent, a combination of cross-calibration and atmospheric correction (Vogelman-DOS3) methods was used. A hybrid supervised/unsupervised classification approach was used to classify the images. Overall accuracies of 94.1% and 93.5% and Kappa Coefficients of 0.908 and 0.913 for the 1986 and 2005 imageries, respectively were obtained. The results showed that 607 km2 of seasonal wetland with low moisture and 22.4 km2 of open water are lost in the study area during the period 1986 to 2005. The current situation in the wetlands of Choke Mountain is characterized by further degradation which calls for wetland conservation and rehabilitation efforts through incorporating wetlands into watershed management plans.

Modelling of root ABA synthesis, stomatal conductance, transpiration and potato production under water saving irrigation regimes

Abstract Application of water saving irrigation strategies in agriculture has become increasingly important. Both modelling and experimental work are needed to gain more insights into the biological and physical mechanisms in the soil–plant system, which regulates water flow in the system and plays a central role in reducing crop transpiration. This paper presented a mechanistic model (Daisy) developed based on data obtained in the SAFIR project on measured leaf gas exchange and soil water dynamics in irrigated potato crops grown in a semi-field environment subjected to different irrigation regimes. Experimental data was compared to simulated results from the new enhanced Daisy model which include modelling 2D soil water flow, abscisic acid (ABA) signalling and its effect on stomatal conductance and hence on transpiration and assimilation, and finally crop yield. The results demonstrated that the enhanced Daisy model is capable of simulating the mechanisms underlying the water saving effects of the partial root-zone drying (PRD) irrigation as compared with the conventional full irrigation (FI). However the simulated effect on both crop yield and water use in this particular experiment was negligible indicating more experimental studies are necessary in order to improve on the model.

Flow regulation for water quality (chlorophyll a) improvement.

In this study a machine learning algorithm was applied in order to develop a predictive model for the changes in phytoplankton biomass (chlorophyll a) in the lower Nakdong River, South Korea. We used a “Hybrid Evolutionary Algorithm (HEA)” which generated model consists of three functions ‘IF-THENELSE’ on the basis of a 15-year, weekly monitored ecological database. We used the average monthly data, 12 years for the training and development of the rule-set model, and the remaining three years of data were used to validate the model performance. Seven hydrological parameters (rainfall, discharge from four multi-purpose dams, the summed dam discharge, and river flow at the study site) were used in the modeling. The HEA selected reasonable parameters among those 7 inputs and optimized the functions for the prediction of phytoplankton biomass during training. The developed model provided accurate predictability on the changes of chlorophyll a (determination coefficients for training data, 0.51; testing data, 0.54). Sensitivity analyses for the model revealed negative relationship between dam discharge and changes in the chlorophyll a concentration. While decreased dam discharge for the testing data was applied; the model returned increased chlorophyll a by 17-95%, and vice versa (a 3-18% decrease). The results indicate the importance of water flow regulation as specific dam discharge is effective to chlorophyll a concentration in the lower Nakdong River.

Soil organic matter dynamics: land use, management and global change

Soil organic matter (SOM) is one of the most complex components of terrestrial ecosystems and serves many vital functions in terms of regulating the flow and supply of nutrients to plants, regulating water flow and water retention in soils and determining the physical attributes of soils. Hence, the maintenance and management of SOM is vital for the sustainability of croplands, grasslands, forests and wetlands. More recently, increased attention has been focused on the role of soils in the global carbon cycle, where the world’s soils contain more than 1.5 trillion tonnes of carbon or roughly three times the carbon contained in all the world’s vegetation and twice the amount of carbon (as CO2) in the earth’s atmosphere. Hence, relatively small changes in the global storage of carbon in SOM can have large effects on greenhouse gas (GHG) concentrations—either positively or negatively. If soils are managed to increase their organic matter content (which also contributes to increased soil fertility), CO2 levels in the atmosphere can be reduced. Currently there is a growing interest in promoting soil carbon sequestration as a GHG mitigation option, particularly in many developing countries. Incorporating carbon sequestration objectives in sustainable land management projects (both via the growing voluntary GHG offset markets and evolving national and international GHG mitigation policies) opens the possibility to radically improve the prospects for improved livelihoods and more sustainable land use practices in developing countries. Research directed at improving our understanding of, and ability to accurately predict, changes in SOM, across the range of managed ecosystems—from croplands, grazing lands, forests and wetlands—is moving very rapidly. Increasingly the science community is being called upon to provide the information and tools needed to support policies directed towards sustainable land use and GHG mitigation, involving SOM. With the overall aim to present the state-of-the-art on SOM studies across the world and highlight future research directions, the International Symposium on Soil Organic Matter Dynamics: Land Use, Management and Global Change was held in Colorado Springs, Colorado, USA, on July 6–9, 2009 (http:// www.nrel.colostate.edu/som-home.html). At the symposium, SOM dynamics were discussed in the context Plant Soil (2011) 338:1–3 DOI 10.1007/s11104-010-0617-6

Aquaporins in the wild: natural genetic diversity and selective pressure in the PIP gene family in five Neotropical tree species.

BackgroundTropical trees undergo severe stress through seasonal drought and flooding, and the ability of these species to respond may be a major factor in their survival in tropical ecosystems, particularly in relation to global climate change. Aquaporins are involved in the regulation of water flow and have been shown to be involved in drought response; they may therefore play a major adaptive role in these species. We describe genetic diversity in the PIP sub-family of the widespread gene family of Aquaporins in five Neotropical tree species covering four botanical families.ResultsPIP Aquaporin subfamily genes were isolated, and their DNA sequence polymorphisms characterised in natural populations. Sequence data were analysed with statistical tests of standard neutral equilibrium and demographic scenarios simulated to compare with the observed results. Chloroplast SSRs were also used to test demographic transitions. Most gene fragments are highly polymorphic and display signatures of balancing selection or bottlenecks; chloroplast SSR markers have significant statistics that do not conform to expectations for population bottlenecks. Although not incompatible with a purely demographic scenario, the combination of all tests tends to favour a selective interpretation of extant gene diversity.ConclusionsTropical tree PIP genes may generally undergo balancing selection, which may maintain high levels of genetic diversity at these loci. Genetic variation at PIP genes may represent a response to variable environmental conditions.

Modelling field scale water partitioning using on-site observations in sub-Saharan rainfed agriculture

Abstract. Smallholder rainfed farming systems generally realise sub-optimal crop yields which are largely attributed to dry spell occurrences during crop growth stages. However, through the introduction of appropriate farming practices, it is possible to substantially increase yield levels even with little and highly variable rainfall. The presented results follow research conducted in the Makanya catchment in northern Tanzania where gross rainfall amounts to less than 400 mm/season which is insufficient to support staple food crops (e.g. maize). The yields from farming system innovations (SIs), which are basically alternative cultivation techniques, are compared against traditional farming practices. The SIs tested in this research are runoff harvesting used in combination with in-field trenches and soil bunds (fanya juus). These SIs aim to reduce soil and nutrient loss from the field and, more importantly, promote in-field infiltration and water retention. Water balance components have been observed in order to study water partitioning processes for the "with" and "without" SI scenarios. Based on rainfall, soil evaporation, transpiration, runoff and soil moisture measurements, a water balance model has been developed to simulate soil moisture variations over the growing season. Simulation results show that, during the field trials, the average productive transpiration flow ranged between 1.1–1.4 mm d−1 in the trial plots compared to 0.7–1.0 mm d−1 under traditional tillage practice. Productive transpiration processes accounted for 23–29% while losses to deep percolation accounted for 33–48% of the available water. The field system has been successfully modelled using the spreadsheet-based water balance 1-D model. Conclusions from the research are that the SIs that were tested are effective in enhancing soil moisture retention at field scale and that diversions allow crop growth moisture conditions to be attained with early rains. From the partitioning analysis, it is also concluded that there is more scope for efficient utilisation of the diverted runoff water if storage structures could be installed to minimise runoff and deep percolation and, hence, regulate water flow to the root zone when required.

Changes of xylem sap ionic content and stem hydraulics in response to irradiance in Laurus nobilis

This study reports experimental evidence for light-mediated changes of stem hydraulic conductance (K(stem)) in field-grown laurel plants. Field measurements based on the evaporative flux method revealed that sun-exposed branches had 60% higher K(stem) with respect to shade-exposed branches. Xylem sap potassium concentration was approximately 3 mM as recorded in shaded branches and up to 12 mM in illuminated ones. Such a difference in [K(+)] proved to induce significant increase in xylem hydraulic conductance of excised twigs when artificially perfused with various solutions, as a likely consequence of the interaction of cations with the pectic matrix of pit membranes (the so-called 'ionic effect'). We propose that this mechanism provides plants with a large potential for fine regulation of water flow towards different parts of the canopy exposed to different environmental conditions with the result of optimizing light and water utilization.

Identifying and prioritising services in European terrestrial and freshwater ecosystems

Ecosystems are multifunctional and provide humanity with a broad array of vital services. Effective management of services requires an improved evidence base, identifying the role of ecosystems in delivering multiple services, which can assist policy-makers in maintaining them. Here, information from the literature and scientific experts was used to systematically document the importance of services and identify trends in their use and status over time for the main terrestrial and freshwater ecosystems in Europe. The results from this review show that intensively managed ecosystems contribute mostly to vital provisioning services (e.g. agro-ecosystems provide food via crops and livestock, and forests provide wood), while semi-natural ecosystems (e.g. grasslands and mountains) are key contributors of genetic resources and cultural services (e.g. aesthetic values and sense of place). The most recent European trends in human use of services show increases in demand for crops from agro-ecosystems, timber from forests, water flow regulation from rivers, wetlands and mountains, and recreation and ecotourism in most ecosystems, but decreases in livestock production, freshwater capture fisheries, wild foods and virtually all services associated with ecosystems which have considerably decreased in area (e.g. semi-natural grasslands). The condition of the majority of services show either a degraded or mixed status across Europe with the exception of recent enhancements in timber production in forests and mountains, freshwater provision, water/erosion/natural hazard regulation and recreation/ecotourism in mountains, and climate regulation in forests. Key gaps in knowledge were evident for certain services across all ecosystems, including the provision of biochemicals and natural medicines, genetic resources and the regulating services of seed dispersal, pest/disease regulation and invasion resistance.

Common pool resource management and PES: Lessons and constraints for water PES in Tanzania

Research into common pool resources from the field and in the laboratory has provided a series of insights for the successful management of such resources. The consequences of action and inaction in managing common pool resources are often most strongly felt (gains or losses) by local people. Several ecosystem services can be considered CPRs but in some cases the benefits of (mis)management are enjoyed by one group while the costs are levied on another group. Here we discuss some of the key findings of the CPR literature and how these relate to key considerations for using PES as a management tool. We focus on the role that ecosystems play in regulating water flows in two basins in Tanzania where feasibility studies have been conducted for the potential implementation of PES for water. We find that the lessons from CPR research shed light on some of the key implementation problems for PES mechanisms, and provide a useful guide for highlighting important user-resource considerations especially in contexts similar to East Africa.

Phenol removal multi cell small water treatment device

A conical one body multi cell, multistage water treatment filtration devices are designed to realize a couple of different processes. Their properties can be used for different technological processes (filtration, ion-exchange, active carbon sorption, etc.). As an example, the devices are studied experimentally for effective technological removal of organic contaminants (phenols) from water using polymeric adsorbents, strong-base anion exchange and active carbon sorption materials. These attempts to combine three processes in one filtration body did show successful results, while the small water treatment devices still being affordably priced. The main contribution of these devices is that they have very compact simple design, simple operative procedures, reduced quantity of valves for treated water and reagent flow regulation. The conical shape of the conical one body multi cell multistage water treatment filtration device ensures linear flow rate to slow down on its path. This hydraulic phenomenon plays a positive role during the sorption processes. The devices could be used as a small water treatment module for local drinking water treatment, etc.

Spatial congruence between biodiversity and ecosystem services in South Africa

Ecosystems services sustain humans all over the world. The unsustainable use of ecosystem services around the world has led to widespread degradation which now threatens human health and livelihoods. Although the maintenance of ecosystem services is often used to justify biodiversity conservation actions, it is still unclear how ecosystem services relate to different aspects of biodiversity and to what extent the conservation of biodiversity will ensure the provision of services. The aim of this study was to find out whether biodiversity priorities, biomes, species richness and vegetation diversity hotspots co-occur in space with ecosystem services. The distribution of the ranges and hotspots of five ecosystem services (surface water supply, water flow regulation, carbon storage, soil accumulation, and soil retention) was assessed in South African biomes. Coincidence, overlap, and correlation analyses were used to assess spatial congruence between ecosystem services and species richness (plants and animals) and vegetation diversity hotspots. The grassland and savanna biomes contained significant amounts of all five ecosystem services. There was moderate overlap and a generally positive but low correlation between ecosystem services hotspots and species richness and vegetation diversity hotspots. Species richness was mostly higher in the hotspots of water flow regulation and soil accumulation than would be expected by chance. The water services showed varying levels of congruence with species richness hotspots and vegetation diversity hotspot. These results indicate that actions taken to conserve biodiversity in South Africa will also protect certain ecosystem services and ecosystem services can be used to strengthen biodiversity conservation in some instances.

Ecosystem Services, Land-Cover Change, and Stakeholders: Finding a Sustainable Foothold for a Semiarid Biodiversity Hotspot

Reyers, B., P. J. O’Farrell, R. M. Cowling, B. N. Egoh, D. C. Le Maitre and J. H. J. Vlok 2009. Ecosystem services, land-cover change, and stakeholders: finding a sustainable foothold for a semiarid biodiversity hotspot. Ecology and Society 14(1): 38. https://doi.org/10.5751/ES-02867-140138

Control of irrigation channels with variable bathymetry and time dependent stabilization rate

This Note deals with the regulation of water flow in open-channels employing the shallow-water model with variable bathymetry. By using energy a priori estimation technics and the compactness theory, we build a stabilizing boundary control. The control law is based on an arbitrary choice of the time dependent stabilization rate r. Say, the energy decreases like the exponential of − ∫ 0 t r ( s ) d s when the time t tends to ∞. To cite this article: A. Sene et al., C. R. Acad. Sci. Paris, Ser. I 346 (2008).

Evaluation of Economic and Hydrologic Impacts of Unified Water Flow Regulation in the Yellow River Basin

Unified water flow regulation has been implemented in the Yellow River, Hei River and Tarim River in China since 1999 as a result of institutional reforms. It has been one of the most important water resources management practices in China during recent years and has generated significant impacts. Based on the data of such an experiment in the Yellow River during 1999 to 2004, a “with-without” scenario analysis method is employed in the paper to evaluate the economic and hydrological impacts of regulation through a holistic model coupling economic water use and hydrologic cycle applied to the study basin. The results show that about 2.5% of GDP was increased every year and the Flow Cutoff Events were avoided as a result of the unified water flow regulation.

Estimation of the detachment rate in eroding rills in flume experiments using an REE tracing method

Rill erosion can be a serious problem on cultivated slopes. Understanding the mechanisms of the detachment process in eroding rills is important in developing and improving process-based erosion prediction models. The detachment rate, defined as the sediment amount detached from a unit area in a unit time, is a crucial parameter in most physical erosion prediction models. Most current studies on rill detachment rates use spatially averaged soil erosion data, which provides little information about soil erosion dynamics due to the lack of spatially distributed, contemporaneous rill erosion data. The objective of this study was to estimate the net detachment rate in eroding rills using a rare earth element (REE) tracing method. Flume experiments were conducted with ten REE oxides (Ho 2O 3, Tb 4O 7, Eu 2O 3, Yb 2O 3, Dy 2O 3, Sm 2O 3, La 2O 3, Tm 2O 3, CeO 2, and Nd 2O 3) as tracers mixed with soil in different sections of five slopes (8.74%, 17.62%, 26.78%, 36.38%, and 46.6%) exposed to three water flow rates (2, 4, and 8 L min − 1 ). Regulated water flow was introduced to the upper end of flumes, 8 m long and 0.1 m wide, which were divided into 10 equal segments, each containing a different REE–soil mixture. The net detachment rate from each rill segment was calculated from the REE concentrations in the eroded and transported material. The detachment rates from different segments along the rills, at different slope gradients and flow rates, were compared with those estimated directly from previous studies, and were found to increase with increasing slope gradient and flow rate. Results also showed that the net rill detachment rates decreased linearly with an increase in sediment concentration, and decreased exponentially with an increase in rill length. The REE-derived detachment data and their relationship with sediment concentrations are consistent with the detachment function used in the WEPP model, and are helpful in understanding the processes of rill erosion. Using REEs to trace detachment rates in continuous rills is a valid and advantageous technique for estimating the spatial distribution of the rill detachment rates.

Use of the water-level fluctuation analysis tool (Regcel) in hydrological status assessment of Finnish lakes

Regulation of water flow constitutes the most important hydromorphological burden to Finnish lakes. The total area of regulated lakes is nearly 11,000 km2, equalling one-third of the total area of Finnish inland waters. Extensive research projects have been carried out since the end of the 1980s to find out opportunities to mitigate harmful effects of the regulation of watercourses. A water-level fluctuation analysis tool, known as Regcel, has been developed to study water level data and to identify the most significant impacts. Results of the Regcel analysis give an overall picture of the impact of lake regulation in northern climate. The model is based on relationships between the water-level fluctuation and factors related to environmental, social and economical effects. Regcel has been used in 12 Lake Regulation Development Projects in Finland. In this article, we show how the Regcel model was applied in two cases.

Effect of Local Soil Hydraulic Conductivity Drop Using a Three‐Dimensional Root Water Uptake Model

The coupling of soil and root water fluxes at the plant scale is a particularly challenging task. Numerical three‐dimensional plant‐scale models exist that consider these soil–root interactions. The influence of the hydraulic conductivity drop at the microscopic scale and especially the effect on root water uptake is not yet assessed in such models. In this study, an analytical approach describing the hydraulic conductivity drop from the bulk soil to the soil–root interface for a three‐dimensional plant‐scale model was derived and validated by numerical means. With these tools, quantification of the local hydraulic conductivity drop with time was possible. Furthermore, the effect of the hydraulic conductivity drop on the time occurrence of plant stress was evaluated. Root water uptake was assessed, with and without considering the hydraulic conductivity drop around single roots in a three‐dimensional plant‐scale model in terms of total water uptake at the root collar under different soil and root properties. It was shown that the total root water uptake was strongly affected, especially under conditions where the radial root hydraulic conductivity, which regulates root water uptake, was larger than the soil hydraulic conductivity, which regulates water flow in the soil. These findings were backed up by numerical validation of the model using mesh refinement. Incorporation of the hydraulic conductivity drop around individual roots in a three‐dimensional plant‐scale model can solve problems with greater accuracy for larger grid resolutions, and with smaller computational times, than not considering the hydraulic conductivity drop.

Maximal stability region of a perturbed nonnegative matrix

AbstractFor a class of positive matrices A+K with a stable positive nominal part A and a structured positive perturbation part K, we address the problem of finding the largest set of admissible perturbations such that the global matrix remains stable. Theoretical bounds are derived and an algorithm for constructing this set is presented. As an example, this algorithm is applied to the regulation of water flow in open channels. Copyright © 2008 John Wiley & Sons, Ltd.

Climate Change and Ecosystems of the Southwestern United States

Arid desert ecosystems of the western United States are particularly susceptible to climate change and climate variability. Plants and animals in this region live near their physiological limits for water and temperature stress. Slight changes in temperature or precipitation regimes or a change in the frequency and magnitude of extreme climatic events could therefore substantially alter the composition, distribution, and abundance of species, as well as the products and services that arid lands provide. In the United States, arid lands are located in the subtropical hot deserts of the Southwest, comprised of the Mojave, Sonoran, and Chihuahuan deserts, and the temperate cold deserts of the Intermountain West. Annual precipitation is low (<400 mm), but the seasonality of precipitation differs substantially among hot deserts (Fig. 1). The Mojave Desert is dominated by winter precipitation; thus biological activity is greatest during the cool season. The Chihuahuan Desert is dominated by summer precipitation with biological activity during hotter conditions. The hottest of the three deserts, the Sonoran, is intermediate, receiving both winter and summer precipitation. Each of these deserts is characterized by low productivity and slow plant growth, both of which are primarily water-limited. Vegetation communities are typically desert scrub, shrub– steppe, or desert grassland/savanna and are home to charismatic plants, including saguaro cacti, organ pipe cacti, and Joshua trees. The Chihuahuan Desert is the largest desert in North America, stretching from the southwestern United States deep into the Central Mexican Highlands. It has been classifi ed by the World Wildlife Fund as a Global 200 Ecoregion, a science-based global ranking of the Earth’s most biologically outstanding habitats. Arid lands currently provide a variety of products and services, including a large ranching industry, wildlife habitat, plant and animal diversity, regulation of water fl ow and quality, opportunities for outdoor recreation, and open spaces for expanding urban environments.