Assessment of environmental flow using morphological characteristics of river (case study: Karoon River, Iran)

Transcription

1 Journal of Bioiversity an Environmental Sciences (JBES) ISSN: (Print) (Online) Vol. 6, No. 4, p , RESEARCH PAPER OPEN ACCESS Assessment of environmental flow using morphological characteristics of river (case stuy: Karoon River, Iran) Mehi Fulaipanah *, Elham Sangi Young Researchers an Elite Club, Ramhormoz Branch, Islamic Aza University, Ramhormoz, Iran Article publishe on April 21, 2015 Key wors: Environmental Flow, Morphological Characteristic, Karoon River. Abstract The relationship between wette perimeter an ischarge is sometimes use as an expeient technique for etermining the minimum flow allowable for environmental purposes. The critical minimum ischarge is suppose to correspon to the point where there is a break in the shape of the curve (usually a logarithmic or power function). Below this ischarge, wette perimeter eclines rapily. The appearance of a break in the shape of the curve is strongly epenent on the relative scaling of the axes of the graph. This subjectivity can be overcome by efining the break in shape using mathematical techniques. The important break in the shape of the curve can be systematically efine by the point where the slope equals 1, or where the curvature is maximize. These two methos were applie to Karoon River, Iran. Seven cross section were selecte. Their survey ata were use to erivate relationship between wette perimeter an ischarge. After etermining breakpoints on the curves, corresponing value of ischarge was calculate from the curves. Analysis of results showe that the slope metho has reasonable an accurate output. Finally, the amount of environmental flow for Karoon river was calculate as cms. * Corresponing Author: Mehi Fulaipanah fulaipanah@gmail.com 303 Fulaipanah an Sangi

2 Introuction Environmental flow may be efine as water that is left in a river system, or release into it, for the specific purpose of managing the conition of that ecosystem. During the last five ecaes, about 100 ifferent approaches have been escribe for avising on environmental flows, an more than 30 countries have begun to use such assessments in the management of water resources (Tharme, 1996; King et al., 1999). There are four main types of flowassessment approaches: hyrological, hyraulic rating, habitat rating, an holistic (King et al., 1999). Those base solely on hyrological ata were among the earliest. They are essentially esktop methos that use summary statistics of flow, which may or may not be ecologically relevant, to avise on suitable flows, often for fish habitat. Because of their lack of sensitivity to iniviual rivers, hyraulic-rating methos were evelope which use fiel measurements to escribe channel-ischarge relationships. Though proviing river-specific ata, these faile to inicate the significance of changes in the measure physical conitions for the aquatic biota. The wette perimeter-ischarge relationship is a basic tool in the transect approach to environmental flow evaluations. One proceure is to erive the relationship from channel cross-section surveys at several ischarge levels. The transects are often locate only at riffle sites, or at sites where fish passage is likely to be limite. Alternatively, the relationship can be moele using the channel morphology, an other ata, using a flow equation such as the Manning equation (Annear an Coner, 1984). A line is generally fitte through the surveye or moele points. The lowest breakpoint in the curve is taken to represent a critical ischarge below which habitat conitions for aquatic organisms (usually fish or macro invertebrates) rapily become unfavorable. The breakpoint inicates where small ecreases in flow result in increasingly greater ecreases in wette perimeter (Goron et al., 1992). IFIM relies heavily on transect ata for physical habitat assessment. While sophisticate hyraulic habitat moeling techniques such as PHABSIM are available, they require etaile hyraulic an morphological surveys, an knowlege of habitat preferences for the species of interest. For these reasons, the simpler approach base on examination of the wette perimeter ischarge relationship is more appropriate in many locations. The wette perimeter ischarge breakpoint has been use to efine optimum or minimum flows for fish rearing (foo prouction) in the US an Australia (Collings, 1974; Cochnauer, 1976; Nelson, 1980; Richarson, 1986). Stalnaker an Arnette reporte that the breakpoints for some US streams occurre at ischarges corresponing to approximately 80% of the maximum available wette perimeter. The Oregon Department of Fish an Willife recommen (among other criteria) that at least 50% of the maximum wette perimeter be provie at riffles (Stalnaker an Arnette, 1976). Filipek et al. foun that for Arkansas streams the breakpoint in the wette perimeter ischarge relationship occurre at 50% of the mean flow. Below this ischarge, riffle areas became expose an unprouctive, stream bank cover for fish iminishe, the water quality ecrease an fish overcrowing was possible (Filipek et al., 1987). For a river in Portugal, Alves also efine the breakpoint as corresponing to a threshol ischarge below which habitat quality becomes significantly egrae (Alves, 1994). For Wyoming an Montana streams, Tennant foun that the flow equivalent to 10% of the average flow provie about 50% of the maximum wette perimeter, while flows greater than 30% of the average flow provie close to the maximum wette perimeter (Tennant, 1976). Nelson foun that wette perimeter curves for streams in Montana ha single, well-efine breakpoints. The ischarges at the breakpoints correspone to the minimum flow levels require to maintain trout populations. Use of multiple transects resulte in less istinct breakpoints (Nelson,1980). Prewitt an Carlson reporte that the wette perimeter approach i not suit the unique fauna of the Upper Colorao River Basin (Prewitt an Carlson, 1977). Smakthin an Eriyagama evelope a 304 Fulaipanah an Sangi

3 software package for global esktop assessment on environmental flows. Their results showe that the software can be use as a tool for rapi preliminary environmental assessment (Smankthin Eriyagama, 2008). Yin an Yang conucte a research about river morphology changes impact on water supply of environmental flow (Yin an Yang, 2012). literature almost universally as a point of inflection. In this paper, wette perimeter metho which has hyraulically basis has been use for Karoon River (Fig. 1). The stuie reach is locate insie the Ahwaz city an has important applicable aspects especially aesthetics an ecological. Therefore, it is necessary to evaluate the minimum require flow in the river for mentione aspects. The hyraulic approach is evelope basically for ecological assessment. This metho is pioneer of avance moels which are use to simulate biological environment (Marchan, 2006). Materials an methos The hyraulic rating methos use changes in hyraulic variables, such as those in the wette perimeter, the area of riverbe submerge, to efine environmental flows. These provie simple inices of available habitat in a river at a given ischarge. The metho is base on the assumption that fish rearing is relate to foo prouction, which is turn is relate to how much of the river be is wet. It uses relationships between wette perimeter an ischarge, epth an velocity to set minimum ischarge for fish foo prouction an rearing (incluing spawning). The relationships are constructe from measuring the length of the wette perimeter at ifferent ischarges in the river of interest. The resulting recommen ischarges are base on the inflection points on the wette perimeter-ischarge curve, which are assume to represent the maximum habitat for minimum flow before the next inflection point. The breakpoint in the wette perimeter versus ischarge relationship (Fig. 2) is referre to in the Fig. 1. Karoon River catchment. The breakpoint on wette perimeter versus ischarge curves that is being sought is not an inflection point, but rather is a point where the curvature is maximize, or where there is a marke change in the slope of the curve. Most people probably try to select the point corresponing to where the tangent to the curve is 45 (i.e. the apparent slope is unity). It is not possible to select this point reliably by eye, since the appearance of the slope of the curve is strongly epenent on the relative scaling of the axes. Variability in the presentation of the graphs will cause inconsistency in the selection of breakpoints. The shape of the relationship between wette perimeter an ischarge is a function of the geometry of the channel, an the manner in which ischarge increases with epth (Gippel an Stewarson, 1998). Defining of Breakpoint One metho of etermining the breakpoint is to select the point on the curve where the slope,, (first erivative y ) equals a nominate value. It is necessary to normalize the two axes to cover the same range. This can be one by expressing each ischarge an wette perimeter value as a proportion of their respective measure or moele maximum values. Alternatively, ischarge may be expresse as a percentage of a flow inex, such as mean annual flow. At the point where the slope of the curve is unity, a 305 Fulaipanah an Sangi

4 small change in ischarge (as a percentage of the maximum value consiere) will prouce the same change in wette perimeter (as a percentage of the maximum value consiere). At higher ischarges where the slope is greater than 1, a large increase in ischarge will prouce a small increase in wette perimeter. At lower ischarges, where the slope is less than 1, a small ecrease in ischarge will prouce a large ecrease in wette perimeter. In this stuy, we ecie to use a slope value of 1 ( y ), but a ifferent slope coul be use to etermine the breakpoint, epening upon the relative values attache to ischarge an habitat area. A secon systematic metho of selecting the breakpoint in the curve is to efine the point of maximum curvature. The curvature (k) is the rate at which a curve turns; it is a function of the angle that the tangent to the curve makes with the x-axis, an the arc length (Gooman, 1980): The y y y an kmax methos give similar breakpoints. The slope metho of selecting the breakpoint is intuitively the most appropriate, an the simplest to apply. The selecte breakpoints for the rectangular channel geometries are close to the bases of the banks. This is appropriate as a minimum ischarge for maintaining flowing water over most of the be. For the trapezoial an triangular channel. geometries, the breakpoint is etermine more by the way ischarge increases with epth (non-linear), than the way the wette perimeter changes with epth (linear). Karoon River is the most important permanent river at the south-west of Iran which has vital ecological an economic roles. In this research, it was selecte to apply wette perimeter approach to evaluate environmental flow. Ahwas station was selecte for calibration an verifying of hyraulic an hyrological ata. Figures 3 an 4 show rating curve an uration flow curve of Ahwaz station. Analysis of aily statics of flow an also flow classification (wet perio, normal perio, ry perio) have been presente in tables 1 an 2, respectively. In the next section, calculation of environmental flow for Karoon river has been one. Results an iscussion Environmental flow assessment in Karoon River has much importance because accoring to Fig. 2, the share of monthly ischarge of Jun. to Dec., which are locate in ry perio, is 35.8% of annual ischarge. This time of year, rive has the less ischarge, an it is necessary to conservation aquatic habitat an vegetation. For application of wette perimeter approach to evaluate environmental flow in Karoon river, Ahwaz station, seven cross sections were selecte which are plotte in figures 5 to 11. Table 1. Flow parameters at Ahwaz station. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Annual Mean STDEV Max Min Table 2. Frequency analysis of Karoon River ischarge Flow parameters at Ahwaz station. Wet perio Mean Dry perio Return perio Discharge (m 3 /s) Fulaipanah an Sangi

5 Three cross sections are locate at ownstream an upstream of Ahwaz station, respectively. The shape of the relationship between wette perimeter an ischarge is a function of the geometry of the channel, an the manner in which ischarge increases with epth. The form of this relationship is accentuate by the way ischarge increases with water epth. At low flows the velocity is low; as epth increases, flow velocity increases, so that ischarge increases at a faster rate than epth. The nature of this relationship is escribe by the Manning equation: n Which Q is ischarge, n is Manning roughness coefficient, A is wette area, R is hyraulic raius, an So is be slope. Roughness coefficient was etermine using geometric characteristics an rating curve of Ahwaz station (Fig. 10). o Table 3. Final results of Wette Perimeter-Discharge approach to evaluate environmental flow. Station Slope metho (y/x=1) Maximum curvature metho Difference: Relative Discharge QEF Relative Discharge Maximum curvature QEF (Ahwaz) Mean STDEV (QEF)Slop-(QEF)Curvature For ifferent values of flow epth, geometric characteristics of channel section an ischarge were calculate from geometric relationship an rating curve, respectively. Using Eq. (2), the value of n was estimate. Its worth noting that longituinal slope, So, was etermine using above seven be elevation. Following etermination of n value, irect step metho was use to verify roughness coefficient. The final result of mentione proceure le to n= Using Manning roughness coefficient an cross sectional profile, relative wette perimeter (P/Pmean) vs. ischarge (Q/Qmean) curve have been plotte for seven cross sections (Figs. 5 to 11). In these figures, x an y axis are relative ischarge an relative wette perimeter, respectively. For each section, relationship between (P/Pmean) an (Q/Qmean) has been etermine. Then, using slope an maximum curvature methos, the graph of slope an curvature vs. relative ischarge was rawn.. For each cross section, the value of <slope=1> an maximum curvature was etermine for specific relative ischarge. The results of calculations are presente at table 3. Fig. 2. Schematic view of breakpoint wette perimeter-ischarge curve. Fig. 3. Rating curve graph of Ahwaz Station. 307 Fulaipanah an Sangi

6 Accoring to table 3, the amount of QEF using slope an curvature metho is between to an 76.1 to m 3.s -1, respectively. Accoring to Fig. 12, these two methos have no goo overlapping, but as it clear, slope metho output is more than curvature metho. Fig. 4. The variation of flow ischarge. Fig. 7. Cross section, Wette perimeter-discharge Graph, Curvature an Slope of wette perimeter relationship for the thir section. Fig. 5. Cross section, Wette perimeter-discharge Graph, Curvature an Slope of wette perimeter relationship for the first section. Fig. 8. Cross section, Wette perimeter-discharge Graph, Curvature an Slope of wette perimeter relationship for the forth section. Fig. 6. Cross section, Wette perimeter-discharge Graph, Curvature an Slope of wette perimeter relationship for the secon section. The environmental flow has ifferent role than the mean flow. On the other han, mean flow has vital role at morphology evelopment whereas 308 Fulaipanah an Sangi

7 environmental flow plays the role of environment protection. Then, the amount of QEF must be less than Qmean. As regars to Fig. 12 an table 2, the amount of environmental flow is etermine as m 3.s -1. techniques, which together prouce a recommene environmental flow regime. This paper provies a metho of overcoming the major problem of subjective interpretation of the breakpoint in the wette perimeter ischarge curve. Provie a curve can be fitte to the ata, the breakpoint of the curve can then be etermine mathematically by calculating the point of maximum curvature or the point where the slope is equal to 1 (or some other selecte value). Of these two approaches, the slope metho is simpler to apply, but requires selection of a suitable slope. Fig. 9. Cross section, Wette perimeter-discharge Graph, Curvature an Slope of wette perimeter relationship for the fifth section. Fig. 11. Cross section, Wette perimeter-discharge Graph, Curvature an Slope of wette perimeter relationship for the seventh section. Fig. 10. Cross section, Wette perimeter-discharge Graph, Curvature an Slope of wette perimeter relationship for the sixth section. Conclusion Using the relationship between wette perimeter an ischarge to etermine minimum environmental flows in regulate streams is problematic, an it shoul only be use in conjunction with other Fig. 12. Comparison between slope an curvature metho for QEF assessment. The suggeste metho of breakpoint etermination can also be applie to curves of flowing water perimeter an fish habitat area as a function of 309 Fulaipanah an Sangi

8 ischarge, provie the habitat variable increases with ischarge over the range of interest. In this paper, wette perimeter-ischarge curve was use to evaluate environmental flow in Karoon River, Iran. Seven cross sections were selecte for this metho. After etermining breakpoint of wette perimeterischarge curve for each cross section, corresponing ischarge of each breakpoint was erive from the curve. The results showe that slope metho has acceptable an reasonable output than the curvature metho. The amount of environmental flow for Karoon river was etermine as m 3.s -1. Accoring to results, hyraulic approach which use characteristics of ecological habitat an river flow can estimate environmental flow with acceptable accuracy. References Alves MH Proceeing a A gua:vii Silubesa, 3, 501. Marchan MD Environmental Flow Requirements for Rivers: An integrate approach for river an coastal zone management, WL Delft Hyraulics. Nelson FA Evaluation of four instream flow methos applie to four trout rivers in southwest Montana, Draft Report to US Fisheries an Willife Ser6ice. Montana Department of Fish Willife an Parks. Nelson FA Evaluation of four instream flow methos applie to four trout rivers in southwest Montana, Montana Department of Fish Willife an Parks. Prewitt CG, Carlson CA Evaluation of four instream flow methoologies use on the Yampa an White Rivers, Colorao, eport to U Fisheries an Willife Ser6ice, Colorao State University. Annear TC, Coner AL Journal of Fish Management 4, 531. Cochnauer T Symposium an Special Conference on Instream Flow Nees 2, 387. Collings MR Generalization of spawning an rearing ischarges for several Pacific salmon species in western Washington, USGS Open File Report. Richarson BA Evaluation of instream flow methoologies for freshwater fish in New South Wales, in Campbell, I.C. E., Water tuies Centre, Chisholm Institute of Technology, Caulfiel. Smankthin VU, Eriyagama N Developing a software package for global esktop assessment of environmental flows. Environmental Moeling an Software 23(12), Filipek S, Keith WE, Giese J Proc. Arkansas Aca. Sci Gippel CJ, Stewarson MJ Regulate Rivers: Research an Management 14(1), 53. Goron ND, McMahon TA, Finlayson BL Stream Hyrology: An Introuction for Ecologists. Wiley, Chichester. King JM, Tharme RE, Brown CA Worl Commission on Dams Thematic Report: efinition an implementation of instream flows,cape Town. Stalnaker CB, Arnette JL Methoologies for etermining instream flows for fish an other aquatic life, Utah State University, Logan. Tennant DL Symposium an Special Conference on Instream Flow Nees 2, 359. Tharme RE Review of international methoologies for the quantification of the instream flow requirements of rivers. Freshwater Research Unit, University of Cape Town. Yin XA, Yang ZF, Proceia Environmental Sciences 13, Fulaipanah an Sangi