The application of satellite radar altimetry to the determination of lake and river elevations has been used in many varying projects, and is a well-validated technique. Here, we show that with the aid of some ancillary ground-based information, this technique can be extended to determine river discharge and predict downstream lake height. The Lake Chad basin provides an ideal case study due to its well-known hydrology, monsoon climate, and because it is situated in a region where water resources are of prime concern. With TOPEX/POSEIDON satellite overpasses across the lake and over the up-stream Chari River, the predictive capability of estimating downstream discharge is of further value. We find that altimetric stage measurements, upstream at the Chari/Ohuam confluence can estimate river discharge about 500 km downstream at N’Djamena and do so 10-days in advance (r2 = 0.9611). Via simple linear correlation methods, the stage measurements can also be used to estimate the height of the permanent waters of the lake (600km downstream) 39 days in advance (r2 = 0.9297). Predicting the water height on the western marshes of the lake-bed is poorer (r2 = 0.7958) due to a change in response time of the local stage to the seasonal floods. Such a change maybe due to a variation in the hydraulic connectivity with the open lake coinciding with an observed increase in mean water level in the latter half of the 1990s. The altimetry proves an additional useful tool where ground-based data is difficult to obtain and where rapid water resource assessment is desirable.