От Адам Redling на 27 юни 2013
http://www.fondriest.com/news/abundant-small-hydropower-dams-more-disruptive-that-large-ones.htm
Ново пет - годишно проучване е довело изследователи от Oregon State University да заключението, че малките водноелектрически проекти могат да окажат отрицателно въздействие върху околната среда повече от големите язовири , поради кумулативната щетите, които те причиняват , според доклад от университета.
Заключението се базира на изследване на речната системата на река Nu в Китай, на която има много малки водноелектрически проекти поради своята многобройни притоци притоци .
Проучването показва, че по-малките водноелектрически проекти имат тенденция да нарушават потока, рибарството , дивата природа и общностите. Това като цяло се дължи на нарушаване на естествения воден поток.
Докладът оценява, че общият ефект върху местообитанията може да бъде 100 пъти по-тежък от изграждането на малки водноелектрически проекти , за разлика от по-големите си колеги.
Самият доклад, можете да прочетете ТУК
Abundant small hydropower dams more disruptive that large ones
Chao Li, Vijay P. Singh and Ashok K. Mishra
Article first published online: 6 JUN 2013 | DOI: 10.1002/wrcr.20146
[1] River flow synthesizing and
downscaling are required for the analysis of risks associated with water
resources management plans and for regional impact studies of climate
change. This paper presents a probabilistic model that synthesizes and
downscales monthly river flow by estimating the joint distribution of
flows of two adjacent months conditional on covariates. The covariates
may consist of lagged and aggregated flow variables (synthesizing),
exogenous climatic variables (downscaling), or combinations of these two
types. The joint distribution is constructed by connecting two marginal
distributions in terms of copulas. The relationship between covariates
and distribution parameters is approximated by an artificial neural
network, which is calibrated using the principle of maximum likelihood.
Outputs of the neural network yield parameters of the joint
distribution. From the estimated joint distribution, a conditional
distribution of river flow of current month given the estimation of the
previous month can be derived. Depending on the different types of
covariate information, this conditional distribution may serve as the
“engine” for synthesizing or downscaling river flow sequences. The idea
of the proposed model is illustrated using three case studies. The first
case deals with synthetic data and shows that the model is capable of
fitting a nonstationary joint distribution. Second, the model is
utilized to synthesize monthly river flow at four sample stations on the
main stream of the Colorado River. Results reveal that the model
reproduces essential evaluation statistics fairly well. Third, a simple
illustrative example for river flow downscaling is presented. Analysis
indicates that the model can be a viable option to downscale monthly
river flow as well.
Development
and testing of a snow interceptometer to quantify canopy water storage
and interception processes in the rain/snow transition zone of the North
Cascades, Washington, USA (pages 3243–3256)Kael A.
Martin, John T. Van Stan II, Susan E. Dickerson-Lange, James A. Lutz,
Jeffrey W. Berman, Rolf Gersonde and Jessica D. Lundquist
Article first published online: 6 JUN 2013 | DOI: 10.1002/wrcr.20271
[1] Tree canopy snow interception is a significant hydrological process, capable of removing up to 60% of snow from the ground snowpack. Our understanding of canopy interception has been limited by our ability to measure whole canopy water storage in an undisturbed forest setting. This study presents a relatively inexpensive technique for directly measuring snow canopy water storage using an interceptometer, adapted from Friesen et al. (2008). The interceptometer is composed of four linear motion position sensors distributed evenly around the tree trunk. We incorporate a trunk laser‐mapping installation method for precise sensor placement to reduce signal error due to sensor misalignment. Through calibration techniques, the amount of canopy snow required to produce the measured displacements can be calculated. We demonstrate instrument performance on a western hemlock (Tsuga heterophylla) for a snow interception event in November 2011. We find a snow capture efficiency of 83 ± 15% of accumulated ground snowfall with a maximum storage capacity of 50 ± 8 mm snow water equivalent (SWE). The observed interception event is compared to simulated interception, represented by the variable infiltration capacity (VIC) hydrologic model. The model generally underreported interception magnitude by 33% using a leaf area index (LAI) of 5 and 16% using an LAI of 10. The interceptometer captured intrastorm accumulation and melt rates up to 3 and 0.75 mm SWE h−1, respectively, which the model failed to represent. While further implementation and validation is necessary, our preliminary results indicate that forest interception magnitude may be underestimated in maritime areas.
Dynamic root distributions in ecohydrological modeling: A case study at Walnut Gulch Experimental Watershed (pages 3292–3305)Gajan Sivandran and Rafael L. Bras
Article first published online: 10 JUN 2013 | DOI: 10.1002/wrcr.20245
[1] Arid regions are characterized by high variability in the arrival of rainfall, and species found in these areas have adapted mechanisms to ensure the capture of this scarce resource. In particular, the rooting strategies employed by vegetation can be critical to their survival. However, land surface models currently prescribe rooting profiles as a function of only the plant functional type of interest with no consideration for the soil texture or rainfall regime of the region being modeled. Additionally, these models do not incorporate the ability of vegetation to dynamically alter their rooting strategies in response to transient changes in environmental forcings or competition from other plant species and therefore tend to underestimate the resilience of these ecosystems. To address the simplicity of the current representation of roots in land surface models, a new dynamic rooting scheme was incorporated into the framework of the distributed ecohydrological model tRIBS+VEGGIE. The new scheme optimizes the allocation of carbon to the root zone to reduce the perceived stress of the vegetation, so that root profiles evolve based upon local climate and soil conditions. The ability of the new scheme to capture the complex dynamics of natural systems was evaluated by comparisons to hourly timescale energy flux, soil moisture, and vegetation growth observations from the Walnut Gulch Experimental Watershed, Arizona. Robust agreement was found between the model and observations, providing confidence that the improved model is able to capture the multidirectional interactions between climate, soil, and vegetation at this site.
Small dams on Chinese river harm environment more than expected
(Phys.org) —A fresh look at the environmental impacts of dams on an ecologically diverse and partially protected river in China found that small dams can pose a greater threat to ecosystems and natural landscapes than large dams.
Read more at: http://phys.org/news/2013-05-small-chinese-river-environment.html#jCp
http://www.fondriest.com/news/abundant-small-hydropower-dams-more-disruptive-that-large-ones.htm
Ново пет - годишно проучване е довело изследователи от Oregon State University да заключението, че малките водноелектрически проекти могат да окажат отрицателно въздействие върху околната среда повече от големите язовири , поради кумулативната щетите, които те причиняват , според доклад от университета.
Заключението се базира на изследване на речната системата на река Nu в Китай, на която има много малки водноелектрически проекти поради своята многобройни притоци притоци .
Проучването показва, че по-малките водноелектрически проекти имат тенденция да нарушават потока, рибарството , дивата природа и общностите. Това като цяло се дължи на нарушаване на естествения воден поток.
Докладът оценява, че общият ефект върху местообитанията може да бъде 100 пъти по-тежък от изграждането на малки водноелектрически проекти , за разлика от по-големите си колеги.
Самият доклад, можете да прочетете ТУК
Abundant small hydropower dams more disruptive that large ones
By Adam Redling on June 27, 2013
A
new five-year study has led researchers from Oregon State University to
conclude that small hydropower projects can negatively impact the
environment more than large dams due to the cumulative damage that they
cause, according to a report from the university.
The
conclusion was based on research of the Nu River system in China, which
supports many small hydroelectric projects because of its expansive
number of tributaries.
The study shows that smaller
hydroelectric projects have a tendency to disrupt streams, fisheries,
wildlife and communities as a whole due to the disruption of natural
water flow.
It was estimated that the total effect on
habitats can be 100 times more severe from the construction of smaller
hydroelectric projects as opposed to their larger counterparts.
Support for low-carbon energy and opposition to new large dams
encourages global development of small hydropower facilities. This
support is manifested in national and international energy and
development policies designed to incentivize growth in the small
hydropower sector while curtailing large dam construction. However, the
preference of small to large dams assumes, without justification, that
small hydropower dams entail fewer and less severe environmental and
social externalities than large hydropower dams. With the objective to
evaluate the validity of this assumption, we investigate cumulative
biophysical effects of small (<50 MW) and large hydropower dams in
China's Nu River basin, and compare effects normalized per megawatt of
power produced. Results reveal that biophysical impacts of small
hydropower may exceed those of large hydropower, particularly with
regard to habitat and hydrologic change. These results indicate that
more comprehensive standards for impact assessment and governance of
small hydropower projects may be necessary to encourage low-impact
energy development.
The original review of macropores and water flow in soils by Beven and Germann
is now 30 years old and has become one of the most highly cited papers
in hydrology. This paper attempts to review the progress in observations
and theoretical reasoning about preferential soil water flows over the
intervening period. It is suggested that the topic has still not
received the attention that its importance deserves, in part because of
the ready availability of software packages rooted firmly in the
Richards domain, albeit that there is convincing evidence that this may
be predicated on the wrong experimental method for natural conditions.
There is still not an adequate physical theory linking all types of
flow, and there are still not adequate observational techniques to
support the scale dependent parameterizations that will be required at
practical field and hillslope scales of application. Some thoughts on
future needs to develop a more comprehensive representation of soil
water flows are offered.
Article first published online: 6 JUN 2013 | DOI: 10.1002/wrcr.20146
Article first published online: 6 JUN 2013 | DOI: 10.1002/wrcr.20271
[1] Tree canopy snow interception is a significant hydrological process, capable of removing up to 60% of snow from the ground snowpack. Our understanding of canopy interception has been limited by our ability to measure whole canopy water storage in an undisturbed forest setting. This study presents a relatively inexpensive technique for directly measuring snow canopy water storage using an interceptometer, adapted from Friesen et al. (2008). The interceptometer is composed of four linear motion position sensors distributed evenly around the tree trunk. We incorporate a trunk laser‐mapping installation method for precise sensor placement to reduce signal error due to sensor misalignment. Through calibration techniques, the amount of canopy snow required to produce the measured displacements can be calculated. We demonstrate instrument performance on a western hemlock (Tsuga heterophylla) for a snow interception event in November 2011. We find a snow capture efficiency of 83 ± 15% of accumulated ground snowfall with a maximum storage capacity of 50 ± 8 mm snow water equivalent (SWE). The observed interception event is compared to simulated interception, represented by the variable infiltration capacity (VIC) hydrologic model. The model generally underreported interception magnitude by 33% using a leaf area index (LAI) of 5 and 16% using an LAI of 10. The interceptometer captured intrastorm accumulation and melt rates up to 3 and 0.75 mm SWE h−1, respectively, which the model failed to represent. While further implementation and validation is necessary, our preliminary results indicate that forest interception magnitude may be underestimated in maritime areas.
Article first published online: 10 JUN 2013 | DOI: 10.1002/wrcr.20245
[1] Arid regions are characterized by high variability in the arrival of rainfall, and species found in these areas have adapted mechanisms to ensure the capture of this scarce resource. In particular, the rooting strategies employed by vegetation can be critical to their survival. However, land surface models currently prescribe rooting profiles as a function of only the plant functional type of interest with no consideration for the soil texture or rainfall regime of the region being modeled. Additionally, these models do not incorporate the ability of vegetation to dynamically alter their rooting strategies in response to transient changes in environmental forcings or competition from other plant species and therefore tend to underestimate the resilience of these ecosystems. To address the simplicity of the current representation of roots in land surface models, a new dynamic rooting scheme was incorporated into the framework of the distributed ecohydrological model tRIBS+VEGGIE. The new scheme optimizes the allocation of carbon to the root zone to reduce the perceived stress of the vegetation, so that root profiles evolve based upon local climate and soil conditions. The ability of the new scheme to capture the complex dynamics of natural systems was evaluated by comparisons to hourly timescale energy flux, soil moisture, and vegetation growth observations from the Walnut Gulch Experimental Watershed, Arizona. Robust agreement was found between the model and observations, providing confidence that the improved model is able to capture the multidirectional interactions between climate, soil, and vegetation at this site.
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