Research Article
Spatial-Temporal Variability of Rainfall over Chitwan District, Nepal
Rajan Khadka*
Issue:
Volume 13, Issue 4, December 2025
Pages:
206-223
Received:
4 October 2025
Accepted:
14 October 2025
Published:
22 November 2025
Abstract: This study analyzes rainfall data (2014–2024) from 10 meteorological stations across Chitwan District to assess spatial-temporal variability. Monsoon (June–September) contributes 78% of annual rainfall, with peaks in July (mean: 435 mm). Pre-monsoon (March–May), post-monsoon (October–November), and winter (December –February) contribute 15%, 4.5%, and 2.5%, respectively. Spatial analysis reveals higher rainfall in northern hills (e.g., Madi: 2,150 mm/yr) versus southern plains (e.g., Bharatpur: 1,400 mm/yr). A significant decreasing trend (-0.82 mm/yr) in annual rainfall was observed. Mann-Kendall tests show 8 stations with declining trends (2 significant). These findings highlight climate vulnerability in a key agricultural region. This study investigates the spatial-temporal variability of rainfall across Chitwan District, Nepal, over the period 2014–2024 using data from ten ground-based meteorological stations. Seasonal and annual rainfall distributions were analyzed to assess long-term changes in precipitation patterns. The results indicate pronounced intra-annual and inter-annual variability, with July recording the highest mean monthly rainfall (644.6 mm) and November the lowest (7.9 mm). The monsoon season (June–September) accounted for approximately 83% of the total annual precipitation, followed by the pre-monsoon (10.7%), post-monsoon (4.1%), and winter (2.2%) seasons. Spatial interpolation using the Inverse Distance Weighted (IDW) method revealed significant heterogeneity in rainfall distribution, with southern forested regions such as Madi and Kalika consistently receiving higher rainfall compared to northern and urban municipalities like Bharatpur and Khairahani. Trend analysis using the non-parametric Mann-Kendall test and Sen’s slope estimator identified a statistically significant decreasing trend in annual rainfall in several central and northern stations, with an average annual decline of 1.03 mm/year across the district. These findings underscore the increasing hydrological vulnerability of Chitwan’s lowland ecosystems and emphasize the need for region-specific water resource planning and climate adaptation measures.
Abstract: This study analyzes rainfall data (2014–2024) from 10 meteorological stations across Chitwan District to assess spatial-temporal variability. Monsoon (June–September) contributes 78% of annual rainfall, with peaks in July (mean: 435 mm). Pre-monsoon (March–May), post-monsoon (October–November), and winter (December –February) contribute 15%, 4.5%, ...
Show More
Research Article
Hydraulic Modeling and Flood Mapping of Flood Plain Along Megech River, Upper Blue Nile Basin, Ethiopia
Masresha Tenaw Demamu*
Issue:
Volume 13, Issue 4, December 2025
Pages:
224-233
Received:
13 October 2025
Accepted:
6 November 2025
Published:
9 December 2025
Abstract: Every year, devastating floods occur in numerous places around the world. Floods are also a daily occurrence in Ethiopia, wreaking havoc and claiming lives, especially in low lying areas such as cities. The Dembia floodplain is one of the most flood-prone districts in Ethiopia. Most victims of flood disasters are people who live in rural areas and make their living from agriculture and livestock near a floodplain. Due to the flooding on the Megech River in Ethiopia, the focus of the study was on hydraulic modeling and flood mapping. Combining the technologies HEC-HMS, HEC-GeoHMS, HEC-RAS and ArcGIS to create a regional model for floodplain identification and representation resulted in floodplain mapping. Using daily time series data, the hydrologic model HEC-HMS was calibrated for return periods of 2, 10, 25, 50, and 100 years. The model HEC-HMS provides 139.7 m3s-1, 228.2 m3s-1, 369.7 m3s-1, 437.8 m3s-1, and 568.8 m3s-1 for return periods of 2, 10, 25, 50, and 100, respectively. A one-dimensional hydraulic model, HEC-RAS, with the HEC-GeoRAS tool extension in ArcGIS was used for flood mapping. The inundation mapping results in 19.92 km2, 23.76 km2, 25.32 km2, 28.65 km2, and 30.09 km2 of inundation area for return periods of 2, 10, 25, 50, and 100, respectively. According to the study, floods have significant impacts as they inundate agricultural and pastoral lands, which has a direct negative impact on of the society. Moreover, flood hazards were evaluated based on the return period and water depth. Therefore, central and local governments should introduce appropriate policies and measures to address this problem.
Abstract: Every year, devastating floods occur in numerous places around the world. Floods are also a daily occurrence in Ethiopia, wreaking havoc and claiming lives, especially in low lying areas such as cities. The Dembia floodplain is one of the most flood-prone districts in Ethiopia. Most victims of flood disasters are people who live in rural areas and ...
Show More
