Reduce surface water abstraction without return

Reduce surface water abstraction without return

Category 01. Water flow quantity improvement

General description

Reducing surface water abstraction without return refers mainly to reductions in water abstraction for agriculture and domestic consumption. We have to distinguish between agriculture without water returns (that uses the water with the maximum efficiency, according to the water needs of the crop) and agriculture with water returns, due to a generous use of water higher than the real water needs of the crop, or inappropriate irrigation techniques. Direct measures for reduce surface water abstraction without return could be:

• Using better adapted crops to the climatic and water availability conditions. The Ecocrop website (FAO) gives useful information for environmental conditions and crop requirements: http://ecocrop.fao.org/ecocrop/srv/en/home
• Using combination of crops that give the same benefits with lower water consumption. For example, replacing the monoculture of cotton by cotton and fodder crops for livestock production was tested in Texas High Plains to reduce the pressure over the Ogallala aquifer (Allen et al., 2005)
• Increase irrigation efficiency by employing the best technology available, fixing water channel and pipes to reduce water loss. Replacing traditional irrigation techniques with low irrigation efficiency when possible (e.g. gravity drainage has a global efficiency of 40-50 % and localized irrigation a global efficiency around 70 – 80 %) or employ these techniques in an optimum way (e.g. in furrow irrigation consider the most suitable slope, furrow length, flow quantity and soil character to reduce drain and percolation and furrow irrigation
• Employing best agricultural practices to reduce water loss by evaporation (e.g. mulching, soil tillage, windbreaks).
• Supply the crops according to their specific water needs. In rainfed farming systems deficit irrigation can provide maximum water use efficiency (WUE) taking into account other factors like sowing date, Nitrogen supply and supplement irrigation level. Maximizing crop production doesn´t necessary maximize the returns per water volume unit. (Oweis et al., 2000).
• Considering land expropriation and the payment of compensations or environmental services for reducing agricultural surface, especially in zones with overexploitation of the resources.

Applicability

There are multiple ways for carrying out this measure, but the common root is the reduction of water demand and water consumption (see Reduce water consumption ). Each alternative has its own constraints, but there is a need of policy support for all of them, especially in southern European countries with problems of water scarcity and droughts. The scale of analysis and application would be most of the times basin or subbasin scale and the scope covers economical, management and political issues parallel to environmental factors. The river basin is generally the base scale to assess the benefits and costs of different water management and infrastructure planning strategies, since it represents the level at which efficient water allocation can be achieved and possible environmental externalities are produced (Pulido-Velazquez et al., 2008). Under the Water Framework Directive water resources allocation should be done efficiently, so it contributes to the achievement of environmental objectives. This allocation should consider not only economic efficiency, but social and environmental efficiency also. From the economic perspective the problem of water flow assignment could be solved prioritizing water uses with higher productivity per cubic meter over those uses with lower productivity. But the application of this principle does not guarantee the equitable distribution of resources: benefits derived from environmental services are difficult to measure and quantify, as well as environmental damages derived from other water uses (e.g. irrigated agriculture). Integrated hydro-economic simulation and optimization models at river basin scales are a useful tool for water assignment and management decisions. They can address environmental and social concerns; represent economic and ecological processes, management alternatives and simulation scenarios. The study of current and expected water uses and demands will inform about the existing alternatives in the definition of future scenarios. Public participation is essential to achieve social acceptance. Agreement between skateholders is an essential task for the development of this measure; otherwise water use limits could be accepted unwillingly and even illegal water abstractions might continue. However it is imperative that public education and involvement are encouraged, so that system complexities and constraints are better understood and overly simplistic solutions avoided (Sophocleous M., 2000).

Expected effect of measure on (including literature citations):

• HYMO (general and specified per HYMO element)

In general, there is expected a positive effect on HYMO elements. Punctual instream abstractions for agriculture and domestic uses haven´t got the same effects as great abstractions and diversions for big reservoir impoundments. The reduction of surface water abstraction would have significant impact on water flow quantity depending on the magnitude of water saved. The main expected effect is an increase of minimum flows (we can say that this is a submeasure that contributes to Increase minimum flows) as most abstractions only affect minimum flows and have negligible effects on variability and flood flows unless there are large upstream storage dams. (Biggs et al., 2008). Anyway the contribution to flow quantity should be seen as part of the whole flow regime, and not separate from flow regime variability. In unregulated rivers, the reduction of the pressure over the streams would enhance the recovery of water flow according to a natural flow regime, but in regulated rivers, the reduction of water abstraction due to water diversions and reservoirs has to consider flow variability.

In “losing” rivers of arid areas, the increase of surface water flow would recharge groundwater aquifer, increase the water level, hyporheic flow and riparian soil humidity that commonly depend on surface water.

Permanent rivers that suffered a transformation into temporal or seasonal rivers may recover their original flow pattern and low flows.

The general increase of water flow quantity would contribute to recover the lateral connectivity of the channel with the riparian zones and the floodplain since a higher water level is expected.

• physico � chemical parameters
• Biota (general and specified per Biological quality elements)

The contribution to low flows would increase habitat quantity; the duration of low flows is sufficient to engender a biological response (Jowett et al. 2005). The type of ecosystem and the linkages between the trophic levels is usually strongly influenced by the overall nature of the flow regime.

BQE	Macroinvertebrates	Fish	Macrophytes	Phytoplankton
Effect	+	++	+	o

Macroinvertebrates:

Depending on the variability of minimum flow increase, macroinvertebrate communities could suffer adverse impact (e.g. a long period of constant minimum flow (2 -3 months) can cause accumulation of periphyton and silt, with the consequent reduction on invertebrate production and diversity (Biggs et al., 2008)). Over the summer, changes to invertebrate communities are linked to an increase in filamentous green algae when the conditions are suitable for their bloom (nutrients and stable flow), causing successional changes on macroinvertebrates communities (Suren et al., 2003).

In unregulated rivers or when an increase on flow quantity occurs along with flow variability, the partial recovery of the natural flow regime will expand the habitable area and thus the production of invertebrates.

Fish:

An increase of habitat availability is expected. Depending on the magnitude, there will be some fish species that will benefit from an increase of water flow. Due to an increase in average velocity and depth at minimum flow, the species preferring fast and /or deep hydraulic conditions will be benefited (increase on usable area and spawning conditions), and higher relative densities are expected (Lamouroux et al., 2006) as a decrease on fish species avoiding fast flows. An increase on summer minimum flow would cause improvement on fish condition (weight and length) and growth length (Weisberg and Burton, 1993).

Macrophytes:

An increase on soil humidity and the water table would benefit aquatic and terrestrial vegetation. It also prevents the occupation of the channel from the vegetation during dry periods.

Phytoplankton:

No significant effect.

Temporal and spatial response

The spatial scope of this measure depends on the scale it is applied, but typically it will be done at local or subbasin scale, and then affect flow quantity at the site and downstream with a cumulative effect.

The temporal response depends on the degree of alteration of the natural conditions and the magnitude of flow quantity change. If the decrease on water quantity was due to land use changes (e.g. from forest to agricultural use) that took place in long time periods (decades to centuries), remediation to reverse impacts will also take a long time, particularly in semiarid regions where the full impact of land use changes has not been realized in many areas (Scalon et al., 2006).

Also, the response of biota will take place in different time scales: macroinvertebrate communities will change in few years while fish communities may change in a period between one year and a decade.

Pressures that can be addressed by this measure

• Surface water abstraction

Case studies where this measure has been applied

• Heltondale Beck Flow restoration

Useful references

Allen V. G. , C. P. Brown, R. Kellison, E. Segarra, T. Wheeler, P. A. Dotray, J. C. Conkwright, C. J. Green and V. Acosta-Martinez. 2005. Integrating Cotton and Beef Production to Reduce Water Withdrawal from the Ogallala Aquifer in the Southern High Plains. Agronomy Journal, 97: 556–567

Biggs B. J. F., R. P. Ibbitt and I.G. Jowett. 2008. Determination of flow regimes for protection of in-river values in New Zealand: an overview. Ecohydrology and Hydrobiology, 8 (1): 17 - 29

Jowett I. G., J. Richardson and M. L. Bonnett. 205. Relationship between flow regime and fish abundances in a gravel‐bed river, New Zealand. Journal of Fosh Biology, 66 (5): 1419 - 1436

Lamouroux N., Olivier J.M., Capra H., Zylberblat M., Chandesris A. and P. Roger. 2006. Fish community changes after minimum flow increase: testing quantitative predictions in the Rhône River at Pierre-Bénite, France. Freshwater Biology 51, 1730–1743

Oweis T., H. Zhang and M. Pala. 2000. Water Use Efficiency of Rainfed and Irrigated Bread Wheat in a Mediterranean Environment. Agronomy Journal, 92:231–238

Pulido-Velazquez M., J. Andreu, A.Sahuquillo and D. Pulido-Velazquez. 2008. Hydro-economic river basin modelling: The application of a holistic surface–groundwater model to assess opportunity costs of water use in Spain. Ecological Economics, 66: 51-65

Scanlon B. R., I. Jolly, M.Sophocleous, and L. Zhang. 2006. Global impacts of conversions from natural to agricultural ecosystems on water resources: Quantity versus quality. Water Resources Research 43, W03437

Sophocleous M. 2000. From safe yield to sustainable development of water resources-the Kansas experience. Journal of Hydrology, 235 (1): 27-43

Suren A. M., B. J. F. Biggs, M. J. Duncan, L. Bergey and P. Lambert. 2003. Benthic community dynamics during summer low-flows in two rivers of contrasting enrichment 2. Invertebrates. New Zealand Journal of Marine and Freshwater Research, 37, (1) : 71 – 83

Weisberg S. B. and W. H. Burton. 1993. Enhancement of Fish Feeding and Growth after an Increase in Minimum Flow below the Conowingo Dam. North American Journal of Fisheries Management , 13: 103-109