Evaluation of Inter-Basin Water Transfer Effects on Superficial Flows in the Donor Basin: Case of Study Upper Course of The Lerma River

The evaluation of inter-basin water transfer (IBWT) effects on superficial flows in the donor basin is based on phases of exploitation of ground water. The phases of exploitation of groundwater proposed in the present work were named: natural state of the river, were there is no alteration by anthropogenic activities on superficial flows; exploitation of groundwater by one type, either by IBWT or by local consumption; and a phase of joint exploitation of groundwater by local consumption an by IBWT, plus a discaharge of waste water from the population in the donor basin to superficial flows. The case of study is the IBWT named Sistema Lerma (SL), which transfer water from the Upper Course of the Lerma River (UCLR) to the valley of Mexico basin since 1951 with an initial flow of 1.65 m³/s (Torres, 2014).

Phase 1 showed a volumetric depletion on superficial flow due to the exploitation of groundwater by the IBWT SL, in relation with natural phase (phase 0). While phase 2 showed a volumetric recuperation respect with phase 1, however, this volumetric increase is due to the discharge of waste water of the population within the UCLR basin, since the concentration of Total Dissolved Solids (TDS) is very close to TDS concentration of tributaries of Lerma River, which in many cases are exclusively of waste water (Fall et all., 2006).

TDS are an indicator of chemical potential energy, so in the present work was found the loos of the potential of superficial flows to albergate an habitat with an ecological flow were endemic species survive, due to the exploitation of ground water by local consumption and by IBWT, plus the discharges of waste water to superficial flows.

Due to the volumetric and energetic variation in the mean flow, a different Unit Emergy Value (UEV) is presented in the average minimum flow in each of the phases, which can be expressed in monetary terms through the Emergy/Money ratio. The variation of the economic equivalent value of the minimum flow showed a decrease of 16.13% in phase 1 in relation to phase 0, while phase 2 showed an increase of 9.01% in relation to phase 1 but a decrease of 8.57% in relation to with the initial phase.