OCR Text |
Show probability is stated as qfy , rather than qfvs ( i. e. by reservoir). This simplification results in the required groundwater demand in the failure years being determined directly as a sum of the uniform annual groundwater yield and the increase in groundwater pumping for that year to make up the surface water shortfall. This may be represented as D - GR + ( l- qfy) XM. y= l.- NY ( 7.8) s- l where Dv is the total groundwater demand for year y, and GR is the annual groundwater firm yield. The decision variables of the model are then Ms, qfy, GR and Qwy- Constraints to bound the total reservoir storage at each site, to ensure that the reservoir is full at the end of the simulation, to bound the yield from each reservoir, to bound the permissible degrees of failure of reservoir yield, to ensure that pumping at wells is adequate to meet the groundwater demand, to maintain aquifer heads, and to bound the well pumpage as well as the groundwater firm yield are then specified. These are stated in order as: T . < T < T ( 7.9) s, mm s s, max v 7 ( 7.10) ( 7.11) ( 7.12) S T s " S s * 0 < s, min M < M s s, max s = 1.. . s Hy * q^ £ q^ yeYf W Amd ^ wy y w= l W s Zm* i ^ wy - GR-( l+ qfy)] TMs £ 0 y= l w= l s= l min H y ** u m i n wy * Hw w= l... W NY ( 7.13) ( 7.14) Qjf1 < Q < Q ™ ax w= l... W, y- l... NY ( 7.15) GR1 < GR < GRU ( 7.16) where Yf is the set of failure years considered, and the other variables are as defined earlier. 172 |