**4.2 Results and discussion**

74 Current Issues of Water Management

**J FMAM J J ASOND MONTH**

Maximum temperature Minimum temp. Mean temp.

(a)

**J FMAM J J A SOND MONTH**

(b) Fig. 3. Pattern of climatic variables for La Paz weather station, (A): maximum, minimum and

mean temperature; (B): rainfall, evaporation and ratio E/P

Rainfall Evaporation Ratio E/P

**RATIO E/P**

**0.0 5.0**

**0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0**

**RAINFALL or EVAPORATION, mm**

**10.0**

**15.0 20.0 25.0 30.0**

**TEMPERATURE,** 

**C**

**35.0 40.0 45.0**

Factors affecting agriculture in Baja California Sur were found to be water deficit (evaporation dramatically exceeds rainfall): 2,380 mm – 180 mm = 2,200 mm of hydrological deficit, water scarcity (evidenced by absence of surface water with groundwater depletion), high temperatures: Temp avg = 24.5, Temp max = 42 C; Salinity (natural and caused), low fertility of soils, and socio-economical factors (long distance form main markets, complex marketing policies, others).

The oriented-extensive ground water extractions have caused notorious water depletion in two out of three contiguous watersheds, at La Paz municipality (Table 2).


Table 2. Hydrological balances for three contiguous watersheds in Baja California Sur, Northwest Mexico

Calculation of the index of water scarcity for La Paz watershed and its four microbasins rendered high values, from 1.11 (microbasin La Palma), to 2.74 (microbasin El Novillo) (Figure 1, Table 3). Results suggest that El Novillo faces a critical condition as a result of high extraction rates, over passing the natural groundwater recharge, with a notorious deficit, estimated in -4,450,068.75 m3, which affects the water availability for urban growth and development.


Table 3. Values of Iwsc calculated for four microbasins of La Paz B.C.S. watershed, Northwest Mexico

The concept of 'sustainable development' as well as 'sustainable agriculture' integrates three main goals: environmental health, economic profitability, and social and economic equity. A variety of philosophies, policies and practices have contributed to these goals. People with many different capacities, from farmers to consumers, have shared this vision. In the case of agriculture, one of the most water-demanding activity, an agroecosystem must be viewed as a source of 'goods' and a sink of 'inputs' (i.e. water). For this activity and for the others, 'nature' (the ecosystem) is the main source of all we consume, but the ecosystem also serves as a sink for all wastes. For production systems, the main resources basically are: water, plants, grains, animals, energy from the sun, wind, and other nonrenewable: oil (from fossil). Human activity is necessarily focused for extracting resources and producing waste to produce, transport to consumer, and dispose of materials. As agriculture and the other socioeconomic activities in arid and semiarid zones depend on water, which mainly is

Assessing Environmental and Social Dimensions of

suppliers and market.

**5. Conclusions** 

Water Issues Through Sustainability Indicators in Arid and Semiarid Zones 77

cycle will be intensified in several zones, with more evaporation and more precipitation, but the extra precipitation will be unequally distributed around the globe. Some parts of the world may see significant reductions in precipitation, or major alterations in the timing of wet and dry seasons (Arnell, 1999). A challenge for scientists is to find appropriate models to diagnose the water deficit, which is the real parameter that impact livestock and agricultural ecosystems. Advanced extensive techniques are so varied and complex that only large areas are feasible and realistic. Most of adapted species to drought do not have yet a real important market, although there are possibilities to develop it. i.e.: *Salicornia bigelovii, Aloe vera, Opuntia spp.* An additional problem is the significant distance from

The study reported here has applied a series of spatially-resolved data sets depicting the biogeophysical and socioeconomic properties of the South-Baja Californian communities in Northwest Mexico. We, as others, have found that Northwest Mexico is a dry zone. Associated with this dryness is a highly dynamic water cycle, providing a large degree of variability in terms of climate, runoff and discharge. A systems perspective is essential to understanding sustainability. The system is envisioned in its broadest sense, from the individual farm, to the local ecosystem, and to communities affected by this farming system, both locally and globally. An emphasis on the system allows a larger and more thorough view of the consequences of farming practices on human communities and the environment. The application and interpretation of sustainability indicators motivates, for the La Paz watershed case, the design and instrumentation of strategies in order to improve the water

A significant fraction of agricultural land and human population is located in the study region with low runoff hydrography at the center of the La Paz valley, with disperse small localities and villages at the high sections of the watershed, with high runoff and high variability. Hence, agricultural water demand defines the aggregate water use for the watershed. These characteristics of human-water interactions, in turn, provide challenges to the water infrastructure of the watershed, with evidences that the region may be experiencing curtailed use of water, relative to its high demands. Biogeophysical data sets, emerging rapidly from the local science community, can make important contributions to

On the base of available evidences, we conclude that both, bio-geophysical as well as socioeconomic indicators will be necessary to map the patterns and intensities of water

This work was financed by the Consejo Nacional de Ciencia y Tecnología (CONACyT), CONACyT-CIENCIA BASICA Fund, Project 134460 "Determinación y construcción de indicadores de la huella hídrica y desertificación como consecuencia de la sobreexplotación agropecuaria y del cambio climático en cuencas de zonas áridas", and by the Centro de Investigaciones Biológicas del Noroeste´ (CIBNOR). Thanks are due to the Comisión Nacional del Agua (CONAGUA), Dirección Local in Baja California Sur, for providing

scarcity. Interdisciplinary study is thus an important component of future research.

use efficiency, and to alleviate the water deficit of the aquifer.

emerging water resource assessments.

climate and geo-hydrological data of La Paz B.C.S.

**6. Acknowledgment** 

obtained from an aquifer, it is crucial to analyze the concept of sustainability of an aquifer: Maintaining a balance between recharge and extraction, or seeking that average annual extraction does not exceed the annual recharge. Although extraction from some groundwater resources has been above the long-term sustainable yield, its use must be managed to the sustainable yield through the implementation of water sharing plans for groundwater (Scanlon, 1997). Current droughts have increased the demand on groundwater resources, causing localized stresses in parts of groundwater systems and overexploitation, with a high risk of water scarcity. A wide variety of ecosystems depend on groundwater for their continued survival. Significant changes in groundwater quality and quantity have the potential to degrade ecosystems and affect human uses of water.

Fig. 4. Geographic and topographic configuration of four microbasins within La Paz BCS watershed, Northwest Mexico, with estimated water deficit, in millions (M) m3

Agriculture and livestock depend on water. Under natural conditions, water deficit is a common condition for agro-ecosystems and grazing-lands in arid zones. "Rainfall" is an important climatic parameter, but in arid and semiarid zones, its analysis scarcely explains the dryness intensity and the aridity pattern. At this stage in earth's history, it is believed that mankind can make 'productive efforts' to decrease or diminish the water depletion, such as artificial groundwater recharge, small dams, artificial infiltration ponds, desalination, increasing the water use efficiency, mitigating or remediating losses, promotion of native agro-forestries for water retention, ad others. In a sort or medium term, the hydrological cycle will be intensified in several zones, with more evaporation and more precipitation, but the extra precipitation will be unequally distributed around the globe. Some parts of the world may see significant reductions in precipitation, or major alterations in the timing of wet and dry seasons (Arnell, 1999). A challenge for scientists is to find appropriate models to diagnose the water deficit, which is the real parameter that impact livestock and agricultural ecosystems. Advanced extensive techniques are so varied and complex that only large areas are feasible and realistic. Most of adapted species to drought do not have yet a real important market, although there are possibilities to develop it. i.e.: *Salicornia bigelovii, Aloe vera, Opuntia spp.* An additional problem is the significant distance from suppliers and market.
