A sensitivity analysis of lake water level response to changes in climate and river regimes

Abstract Lake water level regimes are influenced by climate, hydrology and land use. Intensive land use has led to a decline in lake levels in many regions, with direct impacts on lake hydrology, ecology and ecosystem services. This study examined the role of climate and river flow regime in controlling lake regimes using three different lakes with different hydraulic characteristics (volume-inflow ratio, CIR). The regime changes in the lakes were determined for five different river inflows and five different climate patterns (hot-arid, tropical, moderate, cold-arid, cold-wet), giving 75 different combinations of governing factors in lake hydrology. The input data were scaled to unify them for lake comparisons. By considering the historical lake volume fluctuations, the duration (number of months) of lake volume in different ‘wetness’ regimes from ‘dry’ to ‘wet’ was used to develop a new index for lake regime characterisation, ‘Degree of Lake Wetness’ (DLW). DLW is presented as two indices: DLW₁, providing a measure of lake filling percentage based on observed values and lake geometry, and DLW₂, providing an index for lake regimes based on historical fluctuation patterns. These indices were used to classify lake types based on their historical time series for variable climate and river inflow. The lake response time to changes in hydrology or climate was evaluated. Both DLW₁ and DLW₂ were sensitive to climate and hydrological changes. The results showed that lake level in high CIR systems depends on climate, whereas in systems with low CIR it depends more on river regime

Design of environmental flow regimes to maintain lakes and wetlands in regions with high seasonal irrigation demand

Abstract In arid regions, the construction of dams has led to an increase in irrigated agriculture, resulting in the desiccation of vulnerable lakes and wetlands. In many arid mountainous regions, such as in the Middle East, upstream dams typically feed rivers that flow into lowland terminal (closed) lakes or wetlands. The release of water for environmental purposes is a widely recognised option for reducing such impacts. The present study used monthly hydrological data from the Kor river in southern Iran, its main reservoirs and data above and below the Korbal irrigation system. The Kor river is a major source for feeding the Bakhtegan and Tashk lakes, which have recently started to disappear. An analysis of the water resource system before the dam construction (before 1973) showed that the monthly lake inflow depended on available water in river above the irrigation system (for eight months) and, during the irrigation season, water consumed for irrigation as well (for four months). However, in the post-development period (after 1997), the flow rate to the lake depended almost entirely on the Korbal irrigation system, except during some winter months when little irrigation was needed. Environment flow release has not been effective as it has led to greater water availability in the river, which results in more water being consumed for irrigation, as demonstrated here. To overcome this management mismatch, a new environmental flow release strategy (regime) was designed in which water is released from the upstream reservoirs during periods of low irrigation demand (e.g. winter months)

Coagulation of humic waters for diffused pollution control and the influence of coagulant type on DOC fractions removed

Abstract This study examined the suitability of organic coagulants for treatment of typically humic peat extraction runoff water by comparing their performance with that of ferric sulphate (FS). The influence of coagulant type on dissolved organic carbon (DOC) fractions removed was analysed in detail using LC-OCD-OND (size exclusion liquid chromatography coupled with organic carbon and organic nitrogen detection) fractionation techniques. In general, lower coagulant dosage was needed under acidic (pH 4.5) than neutral (pH 6.5) conditions. Chitosan (Chit) and poly (diallyldimethyl) ammonium chloride (pDMAC) required significantly lower dosage (40–55%) than FS for acceptable purification, while a tannin-based coagulant (Tan2) required substantially higher dosage (55–75%) independent of water pH. FS demonstrated the best removal of DOC (<81%) and phosphorus (<93%) followed by pDMAC, while Chit and Tan2 achieved the highest removal of suspended solids (SS) (<58%), with flocs formed by Tan2 presenting the best settling properties. Higher molecular weight (MW) DOC fractions were more efficiently removed by all coagulants, with FS being the most efficient (biopolymers 69% and humic substances 91%), followed by Tan2. FS also displayed satisfactory removal of lower MW fractions (building blocks ∼46% and low MW neutrals 62%). Overall, FS was the best performing coagulant. Nevertheless, the organic polymers demonstrated satisfactory overall performance, achieving purification rates mostly inside the requirements set by Finnish environmental authorities

Spatiotemporal variability and trends in extreme temperature events in Finland over the recent decades:influence of Northern Hemisphere teleconnection patterns

Abstract Fifteen temperature indices recommended by the ETCCDI (Expert Team on Climate Change Detection and Indices) were applied to evaluate spatiotemporal variability and trends in annual intensity, frequency, and duration of extreme temperature statistics in Finland during 1961–2011. Statistically significant relationships between these high-resolution (10 km) temperature indices and seven influential Northern Hemisphere teleconnection patterns (NHTPs) for the interannual climate variability were also identified. During the study period (1961–2011), warming trends in extreme temperatures were generally manifested by statistically significant increases in cold temperature extremes rather than in the warm temperature extremes. As expected, warm days and nights became more frequent, while fewer cold days and nights occurred. The frequency of frost and icing days also decreased. Finland experienced more (less) frequent warm (cold) temperature extremes over the past few decades. Interestingly, significant lengthening in cold spells was observed over the upper part of northern Finland, while no clear changes are found in warm spells. Interannual variations in the temperature indices were significantly associated with a number of NHTPs. In general, warm temperature extremes show significant correlations with the East Atlantic and the Scandinavia patterns and cold temperature extremes with the Arctic Oscillation and the North Atlantic Oscillation patterns

Expanding the irrigated areas in the MENA and Central Asia:challenges or opportunities?

Abstract Middle Eastern, North African countries (MENA), and Central Asian countries are considered the countries most facing water and food scarcity. The current water exploitation indicates that a few countries are overexploiting their water resources and using the fossil water available. This study reviews each country’s renewable water resources volume and evaluates the resources available to expand the agricultural area. Different scenarios are considered, using both irrigated and rainfed farming options, for concluding the most sustainable farming method in each country. Different scenarios are considered using irrigated and rainfed farming options to recommend the most sustainable farming method for each country. Results show that the countries in the MENA and Central Asia can be divided into three main categories: (1) Countries whose expansion of agricultural area can only be applied by using fossil water resources (Bahrain, Egypt, Kuwait, Libya, Qatar, Saudi Arabia, Turkmenistan, United Arab Emirates, and Uzbekistan); (2) Countries where the agricultural area can be expanded to a certain limit, by sustainably using both irrigated and rainfed farming (Afghanistan, Algeria, Iran, Palestine, Jordan, Kazakhstan, Morocco, Oman, Syria, Tajikistan, Tunisia, and Yemen); (3) Countries that have enough renewable water resources to farm all their agricultural area (Lebanon, Iraq, Turkey, and Kyrgyzstan). However, the aim of this study and its results are only to assess the renewable water resources available to sustain the increased agricultural water demand by setting aside other agricultural factors that constrain the sector

Can limestone, steel slag or man-made sorption materials be used to enhance phosphate-phosphorus retention in treatment wetland for peat extraction runoff with low phosphorous concentration?

Abstract This study examined possibilities to enhance phosphorus (P) retention in wetlands using different materials that could enhance removal of phosphate P (PO₄-P) from runoff waters with fairly low P concentrations (Ptot average 80–90 μg L−1 and PO₄-P 25–30 μg L−1) typical for peat extraction runoff. The retention potential of sorption materials, that had previously shown good retention capacity was first studied in laboratory batch tests using steel slag (basic oxygen furnace slag (BOF)), Filtralite®P (high Ca and Mg clay), CFH 12 (ferrihydroxide), limestone, Phoslock® (95% bentonite clay material + 5% lanthanum) and iron gypsum in year 2010. Based on batch test results and material properties (column tests not suitable for fine clay materials such as Phoslock®), steel slag, CFH 12 and iron gypsum products were selected for column tests. The columns experiments were run for almost three months during spring 2011. Steel slag and Phoslock® were selected for further testing in situ in a treatment wetland. In the laboratory set-ups, all materials tested retained PO₄-P (70–90% in batch tests and approximately 10–80% in column experiments). However, in the field scale set-up, neither steel slag nor Phoslock® successfully retained PO₄-P. The reasons may be e.g. for steel slag, too low pH, too large grain size, and too short retention time. Also, for some set-up, the given instruction were not followed during construction works. Further studies are needed to test different particle sizes and new potential materials for retaining P in treatment wetlands with high hydraulic loading rate, low P concentration and low pH

Defining sustainability in agricultural water management using a Delphi survey technique

Abstract Sustainable water management measures are being developed to address the challenges posed by agriculture runoff and leaching on water resources. These measures are based on experts’ opinions from various sectors and disciplines, ensuring that all stakeholders’ perspectives are considered. For this, establishing a common understanding of ’sustainability’ is essential to avoid misunderstandings, conflicts, and operational challenges. In this research, the Delphi survey technique was utilized to develop a definition of ’sustainability’ in agricultural water management (SAWM) by considering the interdisciplinary group of experts from different parts of the world and those involved in a Horizon 2020 Research and Innovation Action. Twenty-six experts’ perspectives on environmental, economic, and social dimensions of sustainability were assessed, and identified key concepts included climate change, water quality, water availability, stakeholder participation, capacity building, subsidies, and incentives. These concepts were used to define sustainability for multi/interdisciplinary project settings. The definition was validated with consortium members of the project in the regular consortium-wide meetings and used in the respective deliverables dealing with sustainability. The results serve as a foundation for communication between the involved actors and the project’s definition of ’sustainability.’ One recommendation from this work for broader policy formulation for SAWM in Europe is to prioritize farmer needs and focus on environmental sustainability

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

Özet Çok boyutlu olan kuraklık her ne kadar temelde meteorolojik kökenli ise de insan faaliyetlerinin de önemli ölçüde etkilediği bir olaydır. Özellikle yüksek miktarda su isteyen bitkilerin düşük yağış ve yüksek sıcaklık değerlerinin olduğu alanlarda sulama yöntemiyle üretimebaşlanması, öncelikle yer altı suyu seviyesini düşürmekte ardından tarımsal kuraklığa neden olmaktadır. Çalışmaya konu olan Kavardepresyonu (İran) hatalı ürün seçimi ve su noksanlığı nedeniyle günümüzde benzer sorunlarla karşı karşıyadır. Bunu belirlemek amacıyla öncelikle çalışma sahasının 1975–2017 yılları arasındaki arazi kullanımındaki değişimleri ele alınmıştır. Landsat uydu görüntülerinden elde edilen veriler işlenerek çalışma sahasında sulama ile üretimi gerçekleşen alanların zamansal değişimi ortaya konulmuştur. Öte yandan yörenin yağış, sıcaklık, buharlaşma ve su noksanlığı da belirlenmiştir. Ayrıca bölgede ürünlerin hektar başına su kullanım değerlerine de ulaşılmıştır. Böylece arazi kullanımındaki değişimlerin yanında depresyonun iklim elemanlarındaki değişimler de ortaya konulmuştur. Sonuçta 1975’ten günümüze hızla artan sulu tarım alanlarının toplam su istekleri ile depresyonun mevcut su potansiyeli arasındaki ilişki ele alınmış ve bu bağlamda çeşitli çıkarımlarda bulunularak geleceğe yönelik tahminler ve çözüm önerilerinde bulunulmuştur. Çalışmada Landsat 4, 5 ve 8 verileri uzaktan algılama teknikleriyle işlenirken, iklim verileri için nonparamedik Mann-Kendall test korelasyonu ve Thornthwaite Metodu kullanılmıştır.Abstract The multidimensional drought is primarily a meteorological origin. But human activities are also main concern for this scenario, especially in case of irrigation methods when agricultural crops require high amount of water in areas with low rainfall and high temperature. Beacause of this incresing water demand, primarily the groundwater level starts to decrease and hence agricultural drought occures. The Kavar depression in Iran which is the subject of this study also faces problems such as water shortage and the wrong selection of agricultural crop production. In order to determine the facts, the land use changes of the corresponding study area has been taken into account from 1975 to 2017. Different version of Landsat satellite images including Landsat 4, 5 and 8 have been processed by remote sensing techniquesto revealing the temporal variation of the area where the crop was produced by irrigation. However, based on the available rainfall and temperature data, water shortage has been calculated by using Thornthwaite Method. On the other hand, for nonparametric Mann-Kendall test correlation analyses, evaporation data has been used along with other climate data. In addition, water demand per hectare has also been collected for spcific crop of Kavar depression. As a continuation of the analysis based on the natural and artificial elements, finally the relation between the total water demand of irrigated agriculture field and the water potential of depression from 1975 has been found

Recent results from an ecohydrological study of forest species in drained tropical peatlands

Abstract Ecohydrological studies in tropical peatland have mostly focused on a small number of non-native commercial species. However, studies of native species are urgently needed as they are considered to be a possible solution in the restoration of millions of hectares of degraded tropical peatlands. We investigated peatland species on Padang Island, Indonesia, to assess their responses to changing environmental factors, particularly the high fluctuation of the water table due to intensive peatland draining. We monitored the sap-flux velocity and radial growth of six trees (four native and one non-native peatland species) in high temporal resolution using sap-flux meters and dendrometers up to seven months. Monitoring also included hydrological and micrometeorological parameters. We found that sap-flux velocity in the monitored species was mainly controlled by air vapor pressure deficits, photosynthetic active radiation, and to some extent, by wind speed and water-table depth. We also observed a species-specific correlation between daily sap-flux velocity and daily radial growth. Non-native Acacia crassicarpa had up to twice the radial growth of native species. This growth of non-native species was significantly higher at a shallow water-table depth, while native species did not show the same relationship. The interaction between water-table depth, sap-flux velocity, and radial growth in daily timescale was not straightforward, presumably because of the complex carbon-allocation mechanism in trees

A probability-based model to quantify the impact of hydropeaking on habitat suitability in rivers

Abstract A negative effect of hydropower on river environment includes rapid changes in flow and habitat conditions. Any sudden flow change could force fish to move towards a refuge area in a short period of time, causing serious disturbances in the life cycle of the fish. A probability-based model was developed to quantify the impact of hydropeaking on habitat suitability for two fish species, brown trout (Salamo trutta) and Grayling (Thymallus thymallus). The model used habitat preference curves, river velocity and depth to develop the suitability maps. The suitability maps reveal that habitat suitability deteriorates as flow increases in the studied part of the river. The probability model showed that, on average, suitability indices are higher for adult grayling than juvenile trout in hydropeaking events in this part of the river. The method developed shows the potential to be used in river management and the evaluation of hydropeaking impacts in river systems affected by hydropower