Changing rate of urban creep and urban expansion over time and its impact upon the hydrologic response of a catchment

Most previous quantitative research conducted on urban creep and urban expansion has focused on small areas, short time periods, case studies with fairly uniform housing stock and demographic makeup, and the characterisation of urban creep and expansion exclusively in terms of impervious area changes without quantification of the consequential hydrological impact, i.e., increase in surface runoff volume and peak flows in a catchment. This study, using satellite imagery, catchment characteristics data, geographic information system and hydrologic modelling, presents, for the first time, a long-term analysis of urban creep and expansion. The case study is the Ouseburn catchment in Newcastle upon Tyne, a wide-ranging catchment made up of rural, suburban and urban areas, over a period of seven decades. The rate of increase of impervious surfaces is found not to be constant in time; the significant impact of this variation on the catchment's hydrologic response is quantified. This has overall caused a substantial flow volume increase in the Ouseburn over the study period, e.g. 48% for a 1 in 5 years rainfall event. The conclusions obtained are likely representative of many large towns and cities across the United Kingdom and the methodology presented can be easily replicated in other study areas.

Diversity in the observed functionality of dams and reservoirs

Knowledge and modeling of the observed functionality of dams and reservoirs are desirable for better water resources management. In this study, we examine the functionality of dams and reservoirs over much of the globe through a hydroclimate assessment over 990 Global Runoff Data Center stations that have at least one dam/reservoir over the corresponding drainage areas and available streamflow records of at least 25 years. To quantify the potential capacity of human disturbance/alteration, annual cumulative maximum storage (CMS) of the dams are computed and then annual potential changes in the residence time of water (PRT; CMS divided by annual mean monthly flow) are assessed. In addition, the Man-Kendall tests for annual maximum, mean, and minimum monthly streamflow, and drainage area-averaged precipitation are conducted. Results show that the size of CMS and the main purpose have an explanatory power of the designed hydrologic response (i.e., flattening of the seasonality) while 6% of dam-affected stations experienced the opposite hydrologic response (intensifying of the seasonality) due to the overwhelming impact of anthropogenic climate change. This study finds that the magnitude of PRT is a potential indicator to identify a considerable impact of dams and reservoirs for the regional hydrologic regime. The findings of this study suggest diversity in the observed functionality of dams and reservoirs, which is still a challenge in global hydrological modeling.

Prediction of erosion and sedimentation rates using SWAT (Soil and Water Assessment Tool) method in the Jenelata Sub Watershed

Erosion and sedimentation are problems that often occur in watershed ecosystems. The SWAT model (Soil and Water Assessment Tool) can be used to determine the output of a watershed’s performance. Jenelata sub-watershed area is one of the largest sub-watersheds of the Jeneberang watershed with 22.800 ha. This study aims to determine the spatial distribution of the hydrologic response unit (HRU) and analyze the rate of erosion and sedimentation in the Jenelata sub-watershed. The results showed that most HRUs are in secondary dryland forests with 447 HRU (19.09%). The level of erosion in the very light category, namely 5.74 ton/ha/year (37.53%) and light 34.71 ton/ha/year (27.76%), was in the villages of Moncongloe, Tana Karaeng, Sicini, Paladindang, Towata, Parang Lampoa, Manuju, and Buakkang. Meanwhile, moderate erosion was 104.07 ton/ha/year (23.92%), high 289.65 ton/ha/year (9.59%), and very high 553.74 ton/ha/year (1.20%) located in the villages of Pattallikang, Mangempang, Bontomanai, Bissoloro, Rannaloe, Jenebatu, and Sapaya. The largest sedimentation is 133.18 ton/ha/year in sub-watershed17, located in Bissoloro and Rannaloe villages.