Hydrological alterations from water infrastructure development on the Kafue Flats, Zambia

The Kafue River forms a large wetland in southern Zambia called Kafue Flats. This is well known for its high biodiversity providing habitat for many species of wildlife, as well as goods and services to the indigenous communities and urban areas. Since the 1970s water infrastructures were built along the Kafue River to improve Zambian water and energy supply, triggering, at the same time, general concern about the possible threats on the Kafue Flats ecosystem functioning. The construction of a new hydropower scheme in 2016 at ItezhiTezhi Dam, upstream the Kafue Flats, raised the concern about additional changes in hydrological regime with a sub-daily frequency. The main objective of this thesis is to assess the Kafue River hydrological alterations in the first 70 km downstream of the dam and hydropower scheme. To quantify the hydrological alterations (Research Question 1), historical daily discharge data were analyzed with “biological relevant” statistical parameters, using the Range of Variability Approach based on the Indicators of Hydrologic Alteration methods. The analysis at Itezhi-Tezhi and Namwala Pontoon gauging stations indicated a general high level of alteration pre- and post-dam and pre-and post-operating rules changes. The pre- and post-hydropower construction where also analyzed despite the short time series available. Sub-daily water level data obtained during field-work were measured and analyzed (Research question 2). Hydropeaking variations in amplitude and temporal rate decreased along the 70 km reach, until being almost imperceptible. Moreover the hourly water level data ware simulated with a 1D HEC-RAS hydraulic model using two different terrain geometries obtained by a freely available source (SRTM Digital Elevation Model) and field survey (UAV photogrammetry and ADCP bathymetry). The latter performed a better simulation; nevertheless, an overestimation of about 45 cm could be improved by preventing systematic errors during field survey and post-process. Finally remote sensing with Landsat satellite images and Google Earth Engine was used to quantify the maximum flood extent for the hydrological year post-hydropower operation 2016/17 (Research question 3). This was compared with previous flood extents of two hydrological years with similar meteorological conditions (2010/11 and 1996/97). More years will be needed to understand the general trend of the extent in inundated area, since the calculated maximum extent in 2016/17 was less than 2010/11 but similar to 1996/97