International Journal of Hydrology Science and Technology (6 papers in press)

Regular Issues

• Spatiotemporal variability of annual maximum daily precipitation in the Central Zagros Mountains, Iran  
  by Dariush Rahimi, Fatemeh Bashirian, Mehrangiz Solimani 
  Abstract: Thresholds are critical parameters for the functioning of any system. Alterations in thresholds indicate the occurrence of anomalies, and changes in the system. Annual maximum daily precipitation (AMDP) is one of the climatic thresholds that precipitate climate hazards. Changes in extreme precipitation provide evidence of climate change. In this study, the trend of AMDP in the mountainous areas of Central Zagros was examined utilising the Pettitt test (the significance level alpha = 0.05). The AMDP and the ratio of daily precipitation to annual precipitation were analysed during the period 19572023. The test results confirmed the existence of an increasing trend of AMDP at two weather stations: Shahrekourd (43.18%) and Lordegan (39.58%). However, the index of the ratio AMDP to annual precipitation was significant and increased at four weather stations: Shahrekourd (43.60%), Lordegan (38.40%), Borujen (86.47%), Kouhrang (27%). These changes, which have occurred since the 2000s and are more pronounced in the northeast region, have increased the probability of heavy rain and urban flooding. Consequently, flood control management should be reevaluated.
  Keywords: maximum precipitation; extreme value; global warming; Pettitt test; threshold.
  DOI: 10.1504/IJHST.2026.10081376
   
  
• The impact of climate change on precipitation: implications on the intensity duration frequency curves of Calabar metropolis  
  by Nkpa M. Ogarekpe, Charles C. Nnaji 
  Abstract: This study aims to determine the trend in future precipitation in Calabar metropolis, to determine the future change factor of Calabar, as well as to develop a climate change adjusted-intensity duration frequency models for Calabar. The study was carried out using CMIP6 climate models. Global climate model baseline and projected precipitation data were obtained for the periods, spanning 1971-2000 and 2041-2100, respectively. The change factor was determined using the delta change method. On average, the precipitation of the study area is projected to increase by 23% and 39% during the mid-century and end-of century periods, respectively. Average change factor values of 1.3 and 1.4 corresponding to the mid-century and end-of century periods were obtained. The order of magnitude of rainfall intensities for corresponding durations and recurrence intervals are as follows: SSP5_8.5-2,071-2,100 > SSP5_8.5-2041-2070 > stationarity scenario. The study underscores the need for the adoption of non-stationarity IDF relationships for Calabar.
  Keywords: climate change; rainfall; intensity-duration-frequency; model; optimisation.
  DOI: 10.1504/IJHST.2026.10081803
   
  
• New method for studying changes in seepage in earth dams  
  by Leszek Opyrchał, Aleksandra Bąk 
  Abstract: The Pieczyska dam is the highest homogenous hydraulic fill dam in Poland. In 2016, the drain of this dam was renovated. Therefore, it had to be determined whether the seepage conditions in the substrate and the body of the dam had changed. To achieve this goal, statistical methods were used. The correlation coefficient (CC) can be considered as a measure of the co-variance of water levels in the piezometers. If the CC is constant over time, filtration through the dam body and base does not change. A change in the CC is caused by a change in the seepage flow rate or seepage paths. CC of water levels in 82 piezometers and reservoir water level was calculated for two periods: before (years 2008-2015) and after drainage renovation (years 2017-2019). The correlation coefficients of 70% pairs of piezometers remained unchanged in terms of T-Students test. In addition, 30 piezometers out of 82 (i.e., 435 pairs) had a correlation coefficient greater than 0.975. These are located in the middle part of the dam. This proves that infiltration occurs through the abutments but not through the dam body. The work shows how important conclusions regarding the areas of filtration can be drawn with simple statistical calculations.
  Keywords: dam; piezometer; correlation; seepage.
  DOI: 10.1504/IJHST.2026.10081961
   
  
• Mapping agricultural structural hydro-connectivity priorities through a source-pathway-receptor index in the Spercheios River Basin, Greece  
  by Konstantinos Fytilis 
  Abstract: Agricultural pressure reaches rivers only when a source, pathway and receptor coincide. This study developed a parcel-scale Hydro-Connectivity Risk Index (HCRI) for structural screening in the Spercheios River Basin, Greece, using 34,105 active-crop parcels, a 1,019.4-km hydrographic network, terrain, river water bodies and Natura 2000 areas. A 20-m network gate identified 2,225 structurally connected candidates. Source, pathway and receptor components were combined by a weighted geometric mean to limit compensation among weak components. The 10-m connected footprint covered 158.9 ha, of which 75.7% was assigned to high or very-high HCRI classes. Fodder crops, cotton and cereals contributed the largest HCRI-weighted footprint, while GR1831 dominated the sub-basin ranking. Geometric and additive alternatives were strongly correlated but differed for 36 parcels in the highest-ranked fifth. HCRI supports targeted verification and mitigation as a hypothesis-generating screening tool; it does not validate functional connectivity, estimate pollutant loads or demonstrate environmental impact.
  Keywords: agricultural diffuse pollution; GIS; structural hydrological connectivity; source-pathway-receptor; spatial prioritisation; water protection.
  DOI: 10.1504/IJHST.2026.10081962
   
  
• Understanding the impact of geodetic measurements uncertainty on drought assessment: a case study of Europe  
  by Artur Lenczuk, Christopher Ndehedehe, Anna Klos, Janusz Bogusz 
  Abstract: A changing climate reveals that drought are becoming more severe and frequent, with cascading impacts on the environment, and people. As opposed to meteorological-based drought indices, GRACE and GPS observations have provided new capabilities and insights that improve understanding of drought dynamics. However, there are also limitations in the use of geodetic data. Thus, we examine the impact of GRACE and GPS residual errors on defined droughts estimating DSI and its uncertainty based on various approaches. Our results indicate the largest uncertainties above 35 degree. We observe a good spatial consistency in displacement uncertainties between GPS and both GRACE-type data for Western Europe, with relative RMS values over 20%. In comparison to original DSI, uncertainties contain 20% and 100% of DSI signal at 48% and 5% of stations for MSC JPL and GPS, respectively. For TCH method, we identify region-dependent hot spots and north-south strips for displacements and DSI, respectively.
  Keywords: global positioning system; GPS; GRACE; vertical displacements; DSI uncertainty; three-corner hat method; drought.
  DOI: 10.1504/IJHST.2026.10080309
   
  
• Stochastic analyses of climatic variability of Upper Indus Basin, Pakistan  
  by Faisal Nawaz, Syed Ahmad Hassan 
  Abstract: Climate change is one of the major factors affecting Pakistan and the world's ecosystems and is responsible for floods, a massive hydrological problem. Temperature and precipitation influence river flow with complex dynamics in the Karakoram and Himalayan mountainous regions. The objective of this paper is to study the trend analysis of seasonal and monthly rainfall and temperature of six cities: Gilgit, Gupis, Bunji, Astor, Chilas and Skardu in the Upper Indus Basin (UIB). Moreover, this paper also performed downscaling, simulation and prediction of the future scenario over the UIB. The analysis concluded that winter and summer rainfall showed increasing trends in all the cities except Chilas and Gupis, respectively. The fall season had decreasing trends, while the spring had a mix. The observed, statistically downscaled, multiple regression outcomes and their simulated rainfall for two cities, Bunji and Gupis resembled a strong positive correlation.
  Keywords: climate change; trend analysis; temperature; rainfall; river flow hydrology; downscaling; Pakistan.
  DOI: 10.1504/IJHST.2026.10081659