Water Balance, Supply and Demand and Irrigation Efficiency of Indus Basin

Author:IJAZ HUSSAIN, ZAKIR HUSSAIN, MAQBOOL H. SIAL WAQAR AKRAM and M. F. FARHAN
 
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Abstract.

The Indus Basin water is becoming scarce and its demand in rising over for various uses. The water resources statistics is often questionable and based on guesstimates. Keeping in view this assertion, the intent of this paper is to estimate the supply and demand coupled with projections for future in various sectors of economy. The study provides information on water balance and water use efficiency estimate in the competing sectors. The total water available is 274

BCM, of which 130 BCM is available for use, however 62 BCM is lost in the system besides out flow to the sea. The empirical results further revealed that gross water supply for agriculture was nearly 190 BCM while its demand was

210 BCM showing a shortfall of about 20 BCM.

The projected estimates showed that this gap would be further widened by 27

BCM in the year 2015.The crop consumptive use is only 68 BCM and the remaining water is lost in the system. The domestic and Industrial supply and demand showed a shortfall of 5 BCM and 0.15 BCM respectively in the corresponding year. The irrigation application efficiency is 35 percent which abysmally low. Therefore, sound water management strategies are required to increase water productivity, minimize water losses and build a consensus on water dams.

I. INTRODUCTION

There is an increasing demand for water among agricultural, industrial, Municipal, and environmental uses. The water in the Indus Basin was

The authors are, respectively, Graduate Student of Economics at University of Sargodha (Pakistan); Vice-Chancellor, GC University, Faisalabad (Pakistan); Professor/Dean of Faculty of Management Sciences; Graduate Student of Economics at University of Sargodha (Pakistan); and Senior Marketing Specialist, Washington Mutual, San Francisco (USA).

becoming scarce; there was a need to use it efficiently. As there is a high interdependency among uses and users, considerable effort is being placed on improving for integrated management of water resources. As a large consumer of water in irrigation have profound impacts on basin-wide water use and availability. Higher demand from other sectors means reduced supply in irrigation. Irrigation agriculture needs to produce more with less water. Many basins worldwide are facing perceived water shortage due to increasing demands on water from all sectors (Mollinga et al., 2006). It was imperative that basic knowledge about water use and availability was generated in a way that can be useful for policy makers. The water balance approach was useful to provide such information.

Conceptually, the water balance approach was straight forward. Often, though, many components were difficult to estimate and or were not available. For example, ground water inflows and out flows to and from an area of interest are difficult to measure (Mollinga et al., 2006). The water balance was an accounting of the inputs and outputs of water. The water balance of a place, whether it is an agricultural field, watershed, or continent, can be determined by calculating the input, output, and storage changes of water at the Earth’s surface. The major input of water is from precipitation and output is Evapotranspiration. The geographer C. W. Thornthwaite (1899-1963) pioneered the water balance approach to water resource analysis. The author and his team used the water-balance methodology to assess water needs for irrigation and other water-related issues (Ritter, 2006).

The definition of water use efficiency was often misconceived, i.e. if the efficiency was increased there will be a sustainable increase in down stream water use. In general, the major components of the numerator of the unit irrigation efficiency term (Et and Leaching) remain relatively constant for a given series of crops in an area. Improvement in irrigation efficiency occurs mainly as a result of decreasing deliveries. However, much of the water delivered in excess of Evapotranspiration may return to the stream, such changes in efficiency do not result in proportional increases in available water for downstream users. Application of saved water to other lands due to an increase in irrigation efficiency may very well infringe upon a downstream water right. Gross return flow will be less than the losses. The net return flow generally will have higher salt contents (Jensen et al., 1990).

Conceptually, the definition of global efficiency is correct but cannot be seen without the consideration of water quality concerns, which are rather acute in semi-arid and arid environments. The loss of water is not retrievable in the quality context, especially in areas having brackish groundwater. Thus,

global definition of efficiency should be seen in the light of local environments (Ahmed, 2001).

Producing enough food and generating adequate income in the Indus Basin to better feed the poor and reduce the number of those suffering will be a great challenge. This challenge is likely to intensify, with a country’s population that is projected to increase to 250 million in 2025, putting even greater pressure on national food security. Irrigated agriculture has been an important contributor to the expansion of national food supplies since the 1970s and is expected to play a major role in feeding the growing country’s population. However, irrigation accounts for about 90 percent of Indus Basin water withdrawals; and water availability for irrigation may have to be reduced in many areas in favor of rapidly increasing non-agricultural water uses in industry and households, as well as for environmental purposes. With growing irrigation-water demand and increasing competition across water- using sectors, the nation now faces a challenge to produce more food with less water.

This goal will be realistic only if appropriate strategies are found for water savings and for more efficient water uses in agriculture.

The Water Balance provides practitioners with a ‘runoff-based tool’ for source control evaluation and stream health assessment. The ‘runoff-based approach’ holds the key to assessing environmental impacts in watercourses and the effectiveness of mitigation techniques The increase in water demand and complications in managing competing and conflicting water uses require more systematic and comprehensive strategy for managing water resources within the context of localized concepts of efficiency. Thus, the global concepts of efficiency have to be adjusted for the local environments. The statistics of irrigation resources is at best estimates; there is no proper snow management and groundwater regulation. The surface water is not properly monitored; conveyance losses are tremendous and millions of cubic meter water goes to sea.

The efficient use of water in agriculture is not adequately addressed in the country where the sustainability of the existing irrigation system is at stake. While surface irrigation is by far most widely used system in irrigation is practiced on nearly 80 percent of the irrigated area, the most water saving system through micro irrigation is seldomly practiced. Consequently, huge amounts of water diverted for irrigation in the region is wasted at the farm level. However, these losses often represent forgone opportunities for water because they delay the arrival of water at downstream diversion and almost poor quality water. Therefore, it is imperative to have reliable estimates for water resources, use, and efficiency for the Indus Basin. The intent of this

paper is to provide water balance estimates, assess supply and demand situation and estimate water use efficiency.

II. DATA AND METHODOLOGY

The secondary data were taken from government sources such as the Agricultural Statistics of Pakistan, Water and Power Development Authority, Lahore, Pakistan Agricultural Research Council. There are different methods of estimation for water balance, supply and demand projections and water use efficiency.

Assuming the simple and highly restrictive system, which was completely impervious inclined plane surface, confined on all four sides with an outlet at one corner, the water balance equation was written as:

Where

I = inflow per unit time;

O = outflow per unit time; and

ΔS = the change in storage within the system per unit of time.

Δt

WATER BALANCE ABOVE THE SURFACE

Water balance above the surface of the basin was expressed as:

P + R1 – R2 + Rg – Es – Ddi + Fe – I = ΔSs (2)

Water Balance below the surface

Water balance below the surface of the basin can be expressed as:

I + G1 – G2 – Rg – Eb – Et = ΔSg (3)

WATER BALANCE FOR THE INDUS BASIN

Water balance for the basin was expressed by combining the equations (2) and (3).

P – (R2 – R1) – (Es + Eb) – (Et) – (G2 – G1) – Ddi + Fe = Δ(Ss + Sg) (4)

Where

P = Precipitation, M3;

I = Infiltration, M3;

Rg = Groundwater flow that was effluent to a surface stream, M3;

R1 = Runoff as an inflow to the basin, M3;

R2 = Runoff as an outflow from the basin, M3;

G1 = Groundwater flow entering the basin, M3;

G2 = Groundwater as an outflow from the basin, M3;

Es = Evaporation from the surface water bodies or other surface storage areas, M3;

Eb = Evaporation from the bare soil surface, M3;

Et = Evapotranspiration from crops and native vegetation, M3;

Ss = Surface storage, M3;

Sg = Groundwater storage, M3;

Ddi = Water diverted for domestic and industrial uses, M3; and

Fe = Flow of domestic and industrial effluents to the surface streams, M3.

Therefore, the simplified...

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