[...]... names for the water balance equation are Storage Equation, Continuity Equation and Law of Conservation of Mass WaterNet / CCR / ISRI / Catalic / UNESCO-IHE Delft / UZ for UNESCO Course A Basics of Water Resources 18 Several types of water balances can be distinguished, including: • the water balance of the earth surface; • the water balance of a drainage basin; • the water balance of the world oceans;... the water balance of the water diversion cycle (human interference); • the water balance of a local area like a city, a forest, or a polder The water balance of the earth is given in tables 2.1 and 2.2 The water balance of some rivers is given in table 2.3 Table 2.1 Amount of water on earth (Savenije, 2000) Water occurrence 1012 m3 Amount of water % of all water World oceans 1,300,000 97 Salt lakes and... Runoff of the Pungwe at Bue Maria, Mozambique; WaterNet / CCR / ISRI / Catalic / UNESCO-IHE Delft / UZ for UNESCO Course A Basics of Water Resources 25 2.3 Surface water Surface water resources are water resources that are visible to the eye They are mainly the result of overland runoff of rain water, but surface water resources can also originate from groundwater, as was stated in Section 4.1 As Mare... Groundwater feeds surface water and vice versa In the Mupfure catchment in Zimbabwe, Mare (1998) showed that more than 60% of the total runoff of the catchment originated from groundwater Hence most of the water measured at the outfall was groundwater One can say that all renewable groundwater becomes surface water and WaterNet / CCR / ISRI / Catalic / UNESCO-IHE Delft / UZ for UNESCO Course A Basics of. .. groundwater and surface water cannot be separated and although surface water consists to a large extent of groundwater, they are often dealt with separately This is because they have quite different characteristics (time scales, quantities, availability) and because they obey different laws of motion 2.1 The water balance In the field of hydrology the budget idea is widely used Water balances are based... Runoff Runoff Coefficient mm /a Gm3 /a % 30 142 382 935 382 350 86 558 372 795 325 70 14 18 38 70 34 41 WaterNet / CCR / ISRI / Catalic / UNESCO-IHE Delft / UZ for UNESCO Course A Basics of Water Resources 19 Water balance of a drainage basin The water balance is often applied to a river basin A river basin (also called watershed, catchment, or drainage basin) is the area contributing to the discharge at... than 60% of the surface water in the Mupfure basin stemmed from groundwater, a resource hitherto disregarded Surface water is linked to groundwater resources through the processes of infiltration (from surface water to groundwater) and seepage (from groundwater to surface water) Surface water occurs in two kinds of water bodies: • water courses, such as rivers, canals, estuaries and streams; • stagnant... the water flows The water resources of a channel are defined as the total amount of water that passes through the channel over a given period of time (e.g a year, a season, a month) In a given cross-section of a channel the total available amount of surface water runoff over a time step ∆t is defined as the average over time of the discharge R= 1 ∆t t + ∆t ∫ Q dt (2.17) t The discharge Q is generally... groundwater and renews the groundwater On average the percolation minus the capillary rise equals the seepage of groundwater Qg to the surface water The seepage water is clean and does not carry soil particles A river that has clear water carries water that stems from groundwater seepage This is the slow component of runoff During the rise of a flood in a river when the water colour is brown, the water. .. 2000) WaterNet / CCR / ISRI / Catalic / UNESCO-IHE Delft / UZ for UNESCO Course A Basics of Water Resources 8 Integrated Water Resources Management can now be defined as: Integrated Water Resources Management (IWRM) is a process which promotes the coordinated development and management of water, land and related resources, in order to maximise the resultant economic and social welfare in an equitable manner . Course A Basics of Water Resources 6 1.2 Three characteristics of water Water has at least three important physical attributes with a bearing on management:. Course A Basics of Water Resources 8 Integrated Water Resources Management can now be defined as: Integrated Water Resources Management (IWRM) is a