Ali Torabi Haghighi

Defining the natural flow regimes of boreal rivers: relationship with benthic macroinvertebrate communities

Despite the fundamental role of river flow in determining the structure and function of lotic ecosystems, few studies have directly related features of the natural flow regime to variation in stream invertebrate assemblage composition. We classified 240 near-pristine, snowmelt-dominated Finnish streams into hydrological river types. We assessed the relationship of these types with benthic macroinvertebrate assemblage structure and examined the relative importance of hydrological variables, local-habitat variables, and geographical location in predicting variation in assemblage structure. We used a hydrological model to obtain site-specific daily discharges for a 30-y period (1981–2010) and calculated 223 flow indices based on flow index modeling tools. We used a combination of principal component and cluster analysis to classify the sites into 6 distinct hydrological types that were separated mainly by geographical location and catchment-size-related factors. Nonmetric multidimensional scaling and multiresponse permutation procedure showed that macroinvertebrate assemblage structure differed significantly among the hydrological types, but the associated A-statistic indicated wide variation among sites within type. Redundancy analysis indicated that assemblage structure was related more closely to hydrological variables than to local-habitat and spatial variables. The role of hydrology was confirmed further by functional trait structure that showed close relationships to hydrological variables in three-table ordination (RLQ) and fourth-corner analyses. Traits representing organism size and microhabitat preference were correlated most closely with hydrological variables describing variability or seasonality of flows. Our study highlights the role of hydrology in structuring stream assemblages in seasonal, snowmelt-dominated river systems. Modeling hydrological variables in combination with species distribution models may provide a tool for predicting future changes in species distributions in stream ecosystems.

The Quest for Hydrological Signatures: Effects of Data Transformation on Bayesian Inference of Watershed Models

Hydrological models contain parameters, values of which cannot be directly measured in the field, and hence need to be meaningfully inferred through calibration against historical records. Although much progress has been made in the model inference literature, relatively little is known about the effects of transforming calibration data (or error residual) on the identifiability of model parameters and reliability of model predictions. Such effects are analyzed herein using two hydrological models and three watersheds. Our results depict that calibration data transformations significantly influence parameter and predictive uncertainty estimates. Those transformations that distort the temporal distribution of calibration data, such as flow duration curve, normal quantile transform, and Fourier transform, considerably deteriorate the identifiability of model parameters derived in a formal Bayesian framework with a residual-based likelihood function. Other transformations, such as wavelet, BoxCox and square root, while demonstrating some merits in identifying specific model parameters, would not consistently improve predictive capability of hydrological models in a single objective inverse problem. Multi-objective optimization schemes, however, may present a more rigorous basis to extract several independent pieces of information from different data transformations. Finally, data transformations might offer a greater potential to evaluate model performance and assess specific sections of model behavior, rather than to calibrate models in a single objective framework. Findings of this study shed light on the importance and impacts of data transformations in search of hydrological signatures.

Runoff Curve Numbers for Peat-Dominated Watersheds

AbstractThe natural resources conservation service (NRCS) curve number method is widely used to estimate runoff from rainfall events for four hydrological soil groups (A, B, C, and D). However, the NRCS soil groups do not yet include peat soils. Therefore, this study analyzed 59 rainfall-runoff events from two peat-dominated watersheds in Finland (Marjasuo, Royvansuo) and one in Norway (Grualia). The analysis used the United States Army Corps of Engineers Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) to calibrate curve numbers and initial abstraction ratios (Ia/S). This gave a mean Ia/S of 0.036, with a mean standard error of 0.003 and 95% confidence interval of 0.030–0.042, which is significantly lower than the value of 0.2 recommended in the NRCS curve number method. The mean curve number was 61, with a mean standard error of 0.9 and 95% confidence interval of 59–63 for the study watersheds. This study confirmed that application of the NRCS curve number method in HEC-HMS required se...

Effects of Drainage and Subsequent Restoration on Peatland Hydrological Processes at Catchment Scale

Potential benefits of peatland restoration by rewetting include carbon sequestration, restored biodiversity, and improved hydrological functions. There is great uncertainty about how catchment hydrological processes change after restoration, with a particular lack of well-documented catchment runoff data. This study compared five formerly Disturbed (now Restored) and two undisturbed peatlands. In total, 455 and 728 hydrological events were selected for the analysis, using a three-event selection technique. Mean event runoff coefficient (RC) values varied greatly between conditions and hydrological events. RC in Disturbed conditions was slightly higher than in undisturbed conditions, but RC in Restored conditions was higher than under other conditions. Mean transit time revealed that event rainfall water reached the outlet faster in Disturbed conditions. Mean event peak flow in Disturbed conditions was higher and peaked faster than under other conditions. However, the base flow showed no noticeable difference between treatments. Significantly higher watertable (WT) rise per rainfall input (0.36–0.85 cm/mm) was observed in Disturbed conditions, due to lower specific yield (Sy) values (0.13–0.24) than under Restored and undisturbed conditions (Sy 0.25–0.50). Shallow WT showed significant positive correlations with runoff and storage properties and was a key component of the runoff generation mechanisms in peatlands. Storage-related parameters (Sy, WT rise per rainfall input) and catchment response time parameters revealed disturbance-related hydrological changes in peatlands more clearly than other runoff parameters tested (e.g., RC). Overall, with restoration, WT and storage properties recovered to the levels at undisturbed sites but increased runoff was observed occasionally due to wetter antecedent moisture conditions.

Kavar Depresyonu’nda (İran) Arazi Kullanımındaki Değişimler ile Kuraklık Arasındaki İlişkiler

Cok boyutlu olan kuraklik her ne kadar temelde meteorolojik kokenli ise de insan faaliyetlerinin de onemli olcude etkiledigi bir olaydir. Ozellikle yuksek miktarda su isteyen bitkilerin dusuk yagis ve yuksek sicaklik degerlerinin oldugu alanlarda sulama yontemiyle uretime baslanmasi, oncelikle yer alti suyu seviyesini dusurmekte ardindan tarimsal kurakliga neden olmaktadir. Calismaya konu olan Kavar depresyonu (Iran) hatali urun secimi ve su noksanligi nedeniyle gunumuzde benzer sorunlarla karsi karsiyadir. Bunu belirlemek amaciyla oncelikle calisma sahasinin 1975-2017 yillari arasindaki arazi kullanimindaki degisimleri ele alinmistir. Landsat uydu goruntulerinden elde edilen veriler islenerek calisma sahasinda sulama ile uretimi gerceklesen alanlarin zamansal degisimi ortaya konulmustur. Ote yandan yorenin yagis, sicaklik, buharlasma ve su noksanligi da belirlenmistir. Ayrica bolgede urunlerin hektar basina su kullanim degerlerine de ulasilmistir. Boylece arazi kullanimindaki degisimlerin yaninda depresyonun iklim elemanlarindaki degisimler de ortaya konulmustur. Sonucta 1975’ten gunumuze hizla artan sulu tarim alanlarinin toplam su istekleri ile depresyonun mevcut su potansiyeli arasindaki iliski ele alinmis ve bu baglamda cesitli cikarimlarda bulunularak gelecege yonelik tahminler ve cozum onerilerinde bulunulmustur. Calismada Landsat 4, 5 ve 8 verileri uzaktan algilama teknikleriyle islenirken, iklim verileri icin nonparamedik Mann-Kendall test korelasyonu ve Thornthwaite Metodu kullanilmistir.