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Hydrological alteration and biodiversity change along the river network caused by anthropogenic activities and climate variability

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Ecological Processes 2022年第1期11卷 189-205页

作者： Farshid Zolfagharpour Bahram Saghafian majid delavar Department of Civil Engineering Science and Research BranchIslamic Azad UniversityTehranIran Department of Water Resources Engineering Tarbiat Modares UniversityTehranIran

Background:Population growth and intensified human activities in conjunction with climate variability continue to affect the hydrologic cycle,aquatic and terrestrial flora and fauna.In this regard,understanding interactions among ecosystem functions,impacts of anthropogenic interventions and those of climate variability is vital for projecting future ecosystem responses to human activities and climate forcing.The objectives of this study are to determine the ecological flow state via eco-flow index based on discharge hydrograph,to model the ecological diversity through the Shannon diversity index,and to assess the degree of hydrologic alteration using indicators of hydrologic alteration and range of variability approach in six hydrometric stations along the Zayandeh-Rud River in central Iran.The river drains into Gavkhuni Marsh.Also,the streamflow-induced potential changes for Capoeta damascina(a cyprinid fish species of the genus Capoeta),Petroleuciscus esfahani(a small cyprinid fish)and Aphanius isfahanensis(a Cyprinodontid fish)are evaluated.The outcome is expected to assist managers with understanding the effects of anthropogenic activities and climate variability on Gavkhuni aquatic ecosystems so that management options that enhance species resilience and adaptability are outlined.Results:Human activities,a primary factor influencing the natural flow regime,caused a significant increase in the minimum flow,July to March streamflow,low pulse number,and the number of reversals in most studied stations.On the contrary,some other hydrologic indices declined in value.Reservoir impoundment,the most prominent factor among human interventions,resulted in an overall alteration degree of 74.8%in streamflow.Climate variability impacted the natural flow regime in the range of low degree hydrologic alteration(27.3%).In addition,the biodiversity of the study basin,as modeled by the Shannon diversity index,had strong relevance to the annual eco-surplus and was more sensitive to summer floods and autumn hydrological drought

关键词： Eco-flow Shannon diversity index Human activity Indicators of hydrologic alteration Natural flow regime Range of variability Zayandeh-Rud River

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Evaluation of TIGGE Ensemble Forecasts of Precipitation in Distinct Climate Regions in Iran

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Advances in Atmospheric Sciences 2018年第4期35卷 457-468页

作者： Saleh AMINYAVARI Bahram SAGHAFIAN majid delavar Department of Technical and Engineering Science and Research Branch Islamic Azad University Department of Water Resources Engineering Tarbiat Modares University

The application of numerical weather prediction （NWP） products is increasing dramatically. Existing reports indicate that ensemble predictions have better skill than deterministic forecasts. In this study, numerical ensemble precipitation forecasts in the TIGGE database were evaluated using deterministic, dichotomous （yes/no）, and probabilistic techniques over Iran for the period 2008-16. Thirteen rain gauges spread over eight homogeneous precipitation regimes were selected for evaluation. The Inverse Distance Weighting and Kriging methods were adopted for interpolation of the prediction values, downscaled to the stations at lead times of one to three days. To enhance the forecast quality, NWP values were post-processed via Bayesian Model Averaging. The results showed that ECMWF had better scores than other products. However, products of all centers underestimated precipitation in high precipitation regions while overestimating precipitation in other regions. This points to a systematic bias in forecasts and demands application of bias correction techniques. Based on dichotomous evaluation, NCEP did better at most stations, although all centers overpredicted the number of precipitation events. Compared to those of ECMWF and NCER UKMO yielded higher scores in mountainous regions, but performed poorly at other selected stations. Furthermore, the evaluations showed that all centers had better skill in wet than in dry seasons. The quality of post-processed predictions was better than those of the raw predictions. In conclusion, the accuracy of the NWP predictions made by the selected centers could be classified as medium over Iran, while post-processing of predictions is recommended to improve the quality.

关键词： ensemble forecast NWP TIGGE evaluation post-processing

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Simulating long-term effect of Hyrcanian forest loss on phosphorus loading at the sub-watershed level

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Journal of Arid Land 2018年第3期10卷 457-469页

作者： Fatemeh RAJAEI Abbas E SARI Abdolrassoul SALMANMAHINY Timothy O RANDHIR majid delavar Reza D BEHROOZ Alireza M BAVANI Department of Environment Faculty of Natural Resources and Marine Science Tarbiat Modares University Department of Environmental Gorgan University of Agricultural Science & Natural Resources Department of Environmental Conservation University of Massachusetts Department of Water Resources Agriculture Faculty Tarbiat Modares University Department of Environmental Sciences Faculty of Natural Resources University of Zabol Department of Irrigation and Drainage Engineering Faculty of Abouraihan University of Tehran

Conversion of forest land to farmland in the Hyrcanian forest of northern Iran increases the nutrient input, especially the phosphorus（P） nutrient, thus impacting the water quality. Modeling the effect of forest loss on surface water quality provides valuable information for forest management. This study predicts the future impacts of forest loss between 2010 and 2040 on P loading in the Tajan River watershed at the sub-watershed level. To understand drivers of the land cover, we used Land Change Modeler（LCM） combining with the Soil Water Assessment Tool（SWAT） model to simulate the impacts of land use change on P loading. We characterized priority management areas for locating comprehensive and cost-effective management practices at the sub-watershed level. Results show that agricultural expansion has led to an intense deforestation. During the future period 2010–2040, forest area is expected to decrease by 34,739 hm^2. And the areas of pasture and agriculture are expected to increase by 7668 and 27,071 hm^2, respectively. In most sub-watersheds, P pollution will be intensified with the increase in deforestation by the year 2040. And the P concentration is expected to increase from 0.08 to 2.30 mg/L in all of sub-watersheds by the year 2040. It should be noted that the phosphorous concentration exceeds the American Public Health Association′s water quality standard of 0.2 mg/L for P in drinking water in both current and future scenarios in the Tajan River watershed. Only 30% of sub-watersheds will comply with the water quality standards by the year 2040. The finding of the present study highlights the importance of conserving forest area to maintain a stable water quality.

关键词： phosphorus land use change modeling forest loss prioritizing management area Tajan River Iran

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