University of BirjandWater Harvesting Research2476-69769120260301Analysis of Long-Term Changes in Hydro-Climatic Components (Case Study: Maroun Sub-Basin)117390310.22077/jwhr.2026.10877.1198ENMohammadreza RajabiPhD Student, Department of Water Engineering, University of Birjand, Birjand, Iran.Hossein KhozeymehnezhadAssociate Professor, Department of Water Engineering, University of Birjand, Birjand, Iran.Mohammad Nazeri TahroudiAssistant Professor, Department of Water Engineering, Lorestan University, Khorramabad, Iran.Journal Article20251216This research investigates the trends and changes in the statistical distribution of climatic parameters (the warm days index, TX90p, and precipitation) and hydrological parameters (river flow discharge) in the Maroun basin over a 50-year period (1971-2020). The Mann-Kendall test was employed to identify trends, and the Pettitt test was used to determine the timing of abrupt changes. The results indicated that the TX90p index exhibits a statistically significant increasing trend (p-value = 0.018), with a change point in the year 1995, following which its mean value increased by 57%. Although the decreasing trends in precipitation and discharge were not statistically significant at the 95% level, the Pettitt test identified an abrupt change in both parameters in the year 2008. A comparison of the statistical distribution of the data before and after the change points, using Kolmogorov-Smirnov, analysis of variance, and location tests, confirmed that not only the central tendency but also the shape and dispersion of these parameters have changed significantly. Specifically, the mean precipitation and discharge decreased by 28% and 46%, respectively, while their standard deviations also decreased by 38% and 52%, respectively. These findings collectively indicate a shift in the regional climate pattern towards warmer and drier conditions, which has serious implications for water resources management.https://jwhr.birjand.ac.ir/article_3903_f19f9864597038cbce36bfc3bc11e8c6.pdfUniversity of BirjandWater Harvesting Research2476-69769120260301Studying Unsteady Heat and Mass Transfer Condition in a Tubular Solar Still Used for Water Harvesting Implications1827391910.22077/jwhr.2026.11055.1202ENMahdi HedayatizadehAssociate Professor, Faculty of Agriculture, University of Birjand, Birjand, Iran & Member of the Unconventional Water Resources Research Group, University of Birjand, Birjand, Iran.Journal Article20250919 <span class="fontstyle0">This study presents a comprehensive unsteady-state mathematical model for analyzing heat and mass transfer processes in a tubular solar still (TSS), aimed at enhancing the accuracy of temperature predictions and freshwater productivity assessments. The model incorporates time-dependent energy balance equations for key components—including the saline water, trough, humid air, and transparent cover—while accounting for convective, evaporative, radiative, and condensative heat transfer mechanisms. Assumptions such as uniform water temperature, negligible vapor leakage, saturated vapor near the water surface, and minimal solar absorption by humid air are employed to simplify the analysis. Mass transfer coefficients are derived from established correlations, and natural convection is modeled using Rayleigh and Grashof numbers for curved surfaces. Simulations under constant solar radiation (750 W/m²) and ambient temperature (28°C) reveal that the trough exhibits the highest temperature (up to 60°C), followed by saline water, humid air, and the cover (lowest at ~40°C), with all components stabilizing after approximately 2 hours. Cumulative distillate yield reaches approximately 0.5 kg after 8 hours of operation. Parametric analyses demonstrate that a 2.5-fold increase in solar radiation intensity results in a 3.4-fold rise in productivity, while enlarging the diameter from 0.1 m to 0.4 m yields a 4.5-fold enhancement, though at increased cost. The model provides valuable insights for optimizing TSS designs in water-scarce regions, highlighting the potential for sustainable, low-cost desalination.</span> https://jwhr.birjand.ac.ir/article_3919_eca77dba0b73f82e53cfb7d4660bacc4.pdfUniversity of BirjandWater Harvesting Research2476-69769120260301Water Extent Monitoring Using Sentinel-2 (Case Study: Latyan Dam Reservoir)2839392110.22077/jwhr.2026.10498.1191ENAmirhossein MaeliDepartment of Water Engineering, Faculty of Agricultural Technology, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran.Amirali AlaviDepartment of Water Engineering, Faculty of Agricultural Technology, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran.0009-0007-1300-806XEhsan Vasheghani FarahaniDepartment of Water Engineering, Faculty of Agricultural Technology, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran.0000-0002-0228-8314Mahmoud MashalDepartment of Water Engineering, Faculty of Agricultural Technology, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran.Armin NasrollahiDepartment of Water Engineering, Faculty of Agricultural Technology, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran.Journal Article20251116Monitoring the surface area of reservoirs is crucial for effective water resource management, particularly in arid and semi-arid regions where water availability fluctuates significantly. This study utilizes Sentinel-2 imagery to assess water extent variations in the Latyan Dam reservoir in Iran from 2016 to 2024. By applying three well-established water indices—NDWI, MNDWI, & AWEIsh—water surface areas were delineated. Sentinel-2 Level-2A images, preprocessed using the Sen2Cor algorithm, were analyzed in SNAP software, ensuring high accuracy in atmospheric correction and reflectance values. The derived water area was validated using index intersection and union approaches to refine detection accuracy. The reservoir’s surface area showed a clear declining trend, decreasing from 3.3 km² in 2016 (wettest year) to 1.1 km² in 2023 (driest year), corresponding to a shrinkage of about 2.2 km². Throughout 2016–2024, the uncertainty band between the union and intersection of NDWI, MNDWI, and AWEIsh remained relatively narrow, fluctuating between approximately 0.2 and 0.4 km², with slightly lower values in drier years. Applying Otsu thresholding substantially increased the number of uncertain water pixels compared to the fixed global threshold (index ≥ 0), from 3446 to 8250 pixels in 2016 and from 1718 to 7191 pixels in 2023, indicating that the global threshold provides more stable and conservative water detection for long‑term monitoring. This approach provides an efficient, replicable methodology for large-scale water monitoring, supporting sustainable water resource management and policy decisions.https://jwhr.birjand.ac.ir/article_3921_66cc7c95a0f92f31d3c78d94b8bf28c7.pdf