Assessment of Variations in Runoff Due to Landcover Changes Using the SWAT Model in an Urban River in Dublin, Ireland

Investigating the impact of land cover change in hydrological modelling is essential for water resources management. This paper investigates the importance of landcover change in the development of a physically-based hydrological model called SWAT. The study area considered is the Dodder River basin located in southern Dublin, Ireland. Runoff at the basin outlet was simulated using SWAT for 1993–2019 using five landcover maps obtained for 1990, 2000, 2006, 2012 and 2018. Results indicate that, in general, the SWAT model-simulated runoff for a chosen time-period are closer to the real-world observations when the landcover data used for simulation was collated as close to the time-period for which the simulations were performed. For 23 (20) years (from 27 years period) the monthly mean (maximum) runoff for the Dodder River generated by the SWAT model had the least error when the nearby landcover data were used. This study indicates the necessity of considering dynamic and time-varying landcover data during the development of hydrological modelling for runoff simulation. Furthermore, two composite quantile functions were generated by using a kappa distribution for monthly mean runoff and GEV distribution for monthly maximum runoff, based on model simulations obtained using different landcover data corresponding to different time-period. Modelling landcover change patterns and development of projected landcover in the future for river basins in Ireland needs to be integrated with SWAT to simulate future runoff.

Hydrological Effects of Prefabricated Permeable Pavements on Parking Lots

Permeable pavements can infiltrate and reduce stormwater runoff in parking lots, but issues around long construction periods and proper maintenance still required proper research and further understanding. The application of precast concrete can help to solve this. In this study, precast concrete components were applied to the design of permeable pavements to form prefabricated permeable pavements. The laboratory study is one of the first to examine the hydrological effect of prefabricated pervious pavements in parking lots. Four kinds of permeable pavements were designed and manufactured. These had different materials (natural sand-gravel, medium sand) which comprised the leveling layer or different assembly forms of precast concrete at the base. Three scenarios of rainfall intensity (0.5, 1, and 2 mm/min) and three rainfall intervals (one, three, and seven days) were simulated using rainfall simulators. The initial runoff time, runoff coefficient, and runoff control rate of each permeable pavement were investigated during the process of simulating. Results showed that the initial runoff time was no earlier than 42 min, the maximum runoff coefficient was 0.52, and the minimum runoff control rate was 47.7% within the rainfall intensity of 2 mm/min. The initial runoff time of each permeable pavement was no earlier than 36 min when the rainfall interval was one day, whereas, the maximum runoff coefficient was 0.64, and the average runoff control rate was 41.5%. The leveling layer material had a greater impact on the hydrological effect of permeable pavements, while the assembly form of precast concrete had no significant effect. Compared with natural sand-gravel, when the leveling layer was medium sand, the runoff generation was advanced by 4.5–7.8 min under different rainfall intensities, and 7–10 min under different rainfall intervals. The maximum runoff coefficient increased with about 14.6% when the rainfall interval was one day. Among four kinds of permeable pavements, the type I permeable pavement had the best runoff regulation performance. The results revealed that all prefabricated permeable pavements used in this study had good runoff control performance, and this design idea proved to be an alternative for the future design of permeable pavements.

Analisis dan Pemetaan Limpasan Permukaan di DAS Citanduy Hulu dengan Metode SCSN

Abstrak. DAS Citanduy merupakan salah DAS yang terbesar di pulau Jawa dengan sungai utama adalah Cintanduy. DAS Citanduy terdiri dari beberapa sub DAS, salah satunya adalah sub DAS Citanduy Hulu. Perubahan tata guna lahan di DAS Citanduy Hulu terus terjadi, kondisi tsb telah mengakibatkan peningkatan debit banjir di sungai. Peningkatan debit di sungai diakibatkan adanya limpasan permukaan akibat hujan. limpasan permukaan dapat dianalisis menggunakan metode SCS (Soil Conservation Service). Metode SCS juga dianalisis berdasarkan kondisi tanah, sehingga dapat menentukan nilai Curve Number (CN) dari lahan. Hasil analisis tahun 2018, menunjukkan bahwa tutupan lahan 18,99% atau 13.735,97 ha berupa hutan (hutan primer, sekunder dan hutan tanaman). Sebaran jenis tanah di umumnya adalah Typic Dystrudepts (36,57%) dan Typic Hapludands (37,93%). Hydrological Soil Group (HSG) di DAS Citanduy Hulu didominasi oleh klas B sebesar 76, 92 %. Hasil analisis didapatkan bahwa DAS Citanduy Hulu tebal runoff maksimum pada PUH 2, 5, 10, 25, dan 50 tahun secara berurutan adalah 104 mm, 133 mm, 147 mm, 171 mm dan 187 mm. Tebal limpasan permukaan minimum dengan PUH 2, 5, 10, 25 dan 50 tahun secara berurutan adalah 17 mm, 31 mm, 39 mm, 53 mm dan 64 mm. Tebal limpasan permukaan menunjukkan potensi peningkatan debit banjir.Analysis And Mapping Runoff In Watershed Upper Citanduy With SCSN MethodAbstract. Citanduy watershed is one of the largest watersheds on the island of Java with the main river being Cintanduy. The Citanduy watershed consists of several sub-watersheds, one of which is the Upper Citanduy sub-watershed. Changes in land use in the Upper Citanduy watershed continue to occur, this condition has resulted in an increase in flood discharge in the river. The increase in discharge in the river is caused by surface runoff due to rain. Surface runoff can be analyzed using the SCS (Soil Conservation Service) method. The SCS method is also analyzed based on soil conditions so that it can determine the Curve Number (CN) value of the land. The results of the 2018 analysis show that 18.99% or 13,735.97 ha of land cover is forest (primary, secondary and plantation forests). The distribution of soil types, in general, is Typic Dystrudepts (36.57%) and Typic Hapludands (37.93%). Hydrological Soil Group (HSG) in the Upper Citanduy watershed is dominated by class B by 76.92%. The results of the analysis showed that the maximum runoff thickness of the Upper Citanduy Watershed at PUH 2, 5, 10, 25, and 50 years respectively was 104 mm, 133 mm, 147 mm, 171 mm, and 187 mm. The minimum surface runoff thickness with PUH 2, 5, 10, 25, and 50 years respectively is 17 mm, 31 mm, 39 mm, 53 mm, and 64 mm. The thickness of the surface runoff indicates the potential for increased flood discharge.

Statistical analysis of maximum runoff of the Southern Buh River using the method of ‘Indicators of Hydrologic Alteration’

Knowledge of maximum river runoff trends is of great practical importance, especially for design and operation of hydraulic structures. This article presents the results of the research of the Southern Buh River's maximum runoff. The water of the river is widely used for hydropower engineering, industrial and municipal water supply, agriculture, irrigation, shipping, tourism etc. The research of the maximum runoff was based on the Indicators of Hydrologic Alteration (IHA) method which is widely used in the whole world. This method enables calculation of quantitative statistical characteristics of rivers', lakes', reservoirs' runoff and determination of the degree of their hydrological regime changes. The IHA is used for water bodies having natural or regulated runoff. However, the IHA method was not widely used in Ukraine before. The purpose of this publication is using the Indicators of Hydrologic Alterations method in order to study the characteristics of maximum runoff and their changes along the Southern Buh River. The research was carried out based on the data of observations at 5 gauge stations located along the Southern Buh River. The research uses the mean daily discharges that has been recorded since the beginning of observations up to 2018 and 2019 inclusive. The river's runoff at each of gauge stations was divided into five components: "Extremely low runoff", "Low runoff", "High runoff pulses", "Small floods", "Large floods". This made it possible to separate three classes of high (maximum) runoff, for which the IHA statistics were calculated, from the total runoff. It was discovered that the long-term high runoff changes differed in each of its three components, although they had general trends. The most significant changes were found for large floods, with no significant changes found for high runoff pulses. General trends of high runoff showed that over time the values of maximum discharges tend to decrease, with the increasing duration of high runoff periods. The values of the main statistical indicators of high runoff gradually increase from the river's source to its mouth, which fully corresponds to the physical and geographical conditions of its formation. Nevertheless, some features of high runoff were still found. Thus small floods and high runoff pulses have the largest duration in the upper reach of the river. On average, the Southern Buh River experiences large floods once in every 10 years, small floods - once in every 2 years, high runoff pulses - 4-8 times a year in its upper reach and 9-14 times a year in its middle reach.

Assessment of runoff characteristics changes of the left bank tributaries of the Upper Dniester under warming conditions

The inflow of water from the left-bank tributaries of the Upper Dniester is an important component of the runoff formation for the whole river. The study of changes in their water content in the context of global warming is quite urgent and agrees with the provisions of the strategic programme for the Dniester Basin for 2021-2035 aimed at ‘climate change mitigation’ and ‘promoting the principles of sustainable water management’. The paper's objective is to carry out a research into the changes in climatic factors and runoff characteristics that occurred on the left bank of the Upper Dniester in the early 21st century. The research was performed on the basis of hydrometeorological data for the period of 1945-2018. The main research methods include the regression analysis and the method of differential integral curves. It is found that, within the area under study, there is an increase in average annual air temperatures against the background of constant or insignificantly increasing amounts of annual precipitation, thus creating unsatisfactory conditions for runoff formation. It is established that, during the months of cold period, there is an increase in air temperature and that since 1989 the frequency of cases, when the temperature crosses the range of positive values, keeps increasing. 1989 is a turning point in the chronological course of average annual air temperatures; a positive phase of long-term fluctuations starts since that year. With regard to annual precipitation fluctuations from the mid-60s of the last century up to 2013, a positive phase was also identified; within this phase there was a short period of insufficient moisture (1981-1996). It was found that the response of runoff characteristics to climate change was not the same. Maximum runoff during the spring flood is the most sensitive to global warming, since such warming has worsened the conditions for accumulation of water reserves in the snow cover. The transition of maximum runoff fluctuations to the low-water phase took place in 1981. The average long-term decrease in the maximum water flow rates during the spring flood for the period of 1950-2018 amounts to -16.9%. Unlike maximum runoff, the characteristics of the annual and minimum runoff changed gradually during the winter and summer low-water periods and the final transition to the low-water phase of fluctuations occurred only in 2009-2011. Certain inertia of changes in the water resources of Podillya rivers under the warming conditions is caused by the subsurface component making a high contribution to the annual runoff formation (60%). Significant portion of the groundwater supply ‘mitigated’ the effects of surface runoff loss during spring floods. The research allowed establishing the occurrence of statistically significant negative trends in the annual and minimum runoff fluctuations since 1998. If continue to preserve, the identified climate change trends will decrease the inflow of water from the Podillya rivers to the main Dniester River.

Influence of Carbonate-Flysch Contact and Groundwater Dynamics on the Occurrence of Geohazards in Istria, Croatia

This research focuses on the analysis of soil-water interaction at the carbonate-flysch contact on the Istrian peninsula in Croatia. As a result of the interaction of surface and groundwater and the position of flysch and carbonate rocks in the geotechnical profile, two problems occur in the study area: numerous instabilities and the occasionally high turbidity of drinking water. As an example, the St. Ivan spring was considered. The paper presents a complex mechanism of groundwater circulation in geological structures at carbonate-flysch contacts, differences in runoff through karst aquifers and flysch rocks during heavy rainfall under current and predicted (climate change) conditions, and the mentioned geohazards as a result of extreme precipitation. The analyses carried out showed the decisive influence of the existing geological structure on the dynamics of infiltration and precipitation runoff, as well as the risks of pronounced spring water turbidity and instability events. The main drivers of these geohazards are continuous long-term precipitation for landslides and intense daily precipitation for turbidity. Possible consequences of climate change are the increase in precipitation intensity, amount and higher variation, which subsequently brings risks such as the increase in maximum runoff, i.e., the expected more frequent occurrence of high turbidity and the more frequent occurrence of higher cumulative precipitation triggering instabilities in the area.

Features of the Spring Flood Formation in the Arpa River Basin

The article considers main physical and geographical factors affecting the runoff, spring flood of rivers in the Arpa River basin, and analyzes the regularities of their spacetime distribution. The authors have obtained correlation relationship between the values of the flood runoff layer, the mean module maximum runoff and weighted average height of the catchment area of the Arpa River, between the mean annual maximum runoff module for the period floods and catchment areas of rivers. These dependencies can be used for preliminary estimates of the spring flood runoff of unexplored rivers of the territory under consideration. A close correlation between the values of the annual runoff and the runoff of the spring flood in the section of the Arpa River – Dzhermuk has been also revealed. It can be used for forecasting the annual flow.

ASSESSMENT OF THE RIVERS’ MAXIMUM RUNOFF IN THE COASTAL TERRITORY OF PRIMORSKY REGION IN THE VIEW OF FLOODS HAZARD

The temporal patterns and spatial features of the maximum runoff in the coastal territory of Primorsky Region in view of the floods hazard for the period from the beginning of observations to 2018, are considered. The indicator of exceeding the hazardous water level, determined by the territorial divisions of the Hydrometeorology Department of the Russian Federation, used as a criterion for identifying the most flood-prone areas. Except for the Kazachka river, all the considered watercourses are characterized by the predominance of supreme value of runoff in summer-autumn season. There is no dependence between the amplitudes of intra-annual average daily, inter-annual fluctuations of the maximum water levels and the morphometric characteristics of catchments for the rivers on the coast of Primorsky Region. But generally it is obvious that amplitudes grow with increasing a river size. The temporal dynamics of the absolute values of the maximum runoff, its anomalies and long-term water cycles of the rivers in the coastal zone of Primorsky Region are not synchronous, except for a group of neighboring rivers on the east coast, as well as the Razdolnaya river in three gaging stations. The rivers of the coast region are characterized by a complex spatial differentiation of hazardous phenomena associated with high water levels. Their recurrence differs on closely located rivers. An increase in the frequency of floods in recent years has been observed only on certain rivers as the Razdolnaya river at Novogeorgievka settlement and the Rakovka river at Opyitny settlement. The territories of the catchments of the Razdolnaya, Borisovka and Tsukanovka rivers are exposed to the greatest threats of exceeding the hazardous water levels